The Netter Collection of Medical Illustrations VOLUME 9 Digestive System Part I - The Upper Digestive Tract ( PDFDrive )_compressed

The Netter Collection

OF MEDICAL ILLUSTRATIONS

Digestive System

Part I—Upper Digestive
Tract

2nd Edition

A compilation of paintings prepared by
FRANK H. NETTER, MD

Editor Associate Editors

James C. Reynolds, MD David A. Katzka, MD

June F. Klinghoffer Distinguished Professor of Medicine
Professor and Chair Mayo Clinic
Rochester, Minnesota
Department of Medicine
Drexel University College of Medicine Henry P. Parkman, MD
Philadelphia, Pennsylvania
Professor of Medicine
Senior Associate Editor Director, GI Motility Laboratory
Temple University School of Medicine
Peter J. Ward, PhD Philadelphia, Pennsylvania

Associate Professor of Anatomy Michele A. Young, MD
Department of Biomedical Sciences
West Virginia School of Osteopathic Assistant Professor of Clinical Medicine
University of Arizona School of
Medicine
Lewisburg, West Virginia Medicine–Phoenix
Associate Chief of Gastroenterology
Associate Chief of Medicine–

Gastroenterology
Phoenix Veterans Administration Health

Care System
Phoenix, Arizona

Additional Illustrations by Carlos A.G. Machado, MD

CONTRIBUTING ILLUSTRATORS
John A. Craig, MD
Tiffany S. DaVanzo, MA, CMI
Kristen Wienandt Marzejon, MS, MFA
James A. Perkins, MS, MFA

1600 John F. Kennedy Blvd.
Ste. 1800
Philadelphia, PA 19103-2899

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS ISBN: 978-1-4557-7390-9
DIGESTIVE SYSTEM: PART I—UPPER DIGESTIVE TRACT,
VOLUME 9, SECOND EDITION

Copyright © 2017 by Elsevier Inc.

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Last digit is the print number:  9  8  7  6  5  4  3  2  1

ABOUT THE SERIES

Dr. Frank Netter at work. Dr. Frank H. Netter exemplified the CUSHING’S SYNDROME IN A PATIENT WITH THE CARNEY COMPLEX
The single-volume “blue book” that paved the way for distinct vocations of physician,
the multivolume Netter Collection of Medical Illustrations artist, and teacher. Even more important— Carney complex is characterized
series aff ectionately known as the “green books.” he unified them. Netter’s illustrations by spotty skin pigmentation.
always began with meticulous research Pigmented lentigines and blue
into the detailed human clinical nevi can be seen on the face–
anatomy and pathology, a philosophy including the eyelids, vermillion
that steered his broad and deep medical borders of the lips, the
understanding. He often said: “Clarifi­ conjunctivae, the sclera–and the
cation is the goal. No matter how beau­ labia and scrotum.
tifully painted, a medical illustration Additional features of the
has little value if it does not make clear Carney complex can include:
a medical point.” His greatest challenge
and greatest success was charting a Myxomas: cardiac atrium,
middle course between artistic clarity cutaneous (e.g., eyelid),
and instructional complexity. That suc­ and mammary
cess is captured in this series, beginning Testicular large-cell
in 1948, when the first comprehensive calcifying Sertoli cell tumors
collection of Netter’s work, a single Growth-hormone
volume, was published by CIBA Pharmaceuticals. It secereting pituitary adenomas
met with such success that over the following 40 years Psammomatous
the collection was expanded into an 8-volume series— melanotic schwannomas
each devoted to a single body system.
In this second edition of the legendary series, we are PPNAD adrenal glands are usually of normal size and most are
delighted to offer Netter’s timeless work, now arranged studded with black, brown, or red nodules. Most of the pigmented
and informed by modern text and radiologic imaging nodules are less than 4 mm in diameter and interspersed in the
contributed by highly respected neurologic authorities adjacent atrophic cortex.
from world-renowned medical institutions, and supple­
mented with new illustrations created by artists working A brand new illustrated plate painted by Carlos Machado,
in the Netter tradition. Inside the classic green covers, MD, for The Endocrine System, Volume 2, 2nd ed.
students and practitioners will find hundreds of original
works of art—the human body in pictures—paired with Dr. Carlos Machado at work.
the latest in expert medical knowledge and innovation
and anchored in the sublime style of Frank Netter.
Noted artist-physician, Carlos Machado, MD, the
primary successor responsible for continuing the Netter
tradition, has particular appreciation for the Green Book
series. “The Reproductive System is of special significance
for those who, like me, deeply admire Dr. Netter’s work.
In this volume, he masters the representation of textures
of different surfaces, which I like to call ‘the rhythm of
the brush,’ since it is the dimension, the direction of the
strokes, and the interval separating them that create the
illusion of given textures: organs have their external
surfaces, the surfaces of their cavities, and texture of their
parenchymas realistically represented. It set the style for
the subsequent volumes of Netter’s Collection—each an
amazing combination of painting masterpieces and
precise scientific information.”
Though the science and teaching of medicine endures
changes in terminology, practice, and discovery, some
things remain the same. A patient is a patient. A teacher
is a teacher. And the pictures of Dr. Netter—he called
them pictures, never paintings—remain the same blend
of beautiful and instructional resources that have guided
physicians’ hands and nurtured their imaginations for
more than half a century.
The original series could not exist without the dedica­
tion of all those who edited, authored, or in other ways
contributed, nor, of course, without the excellence of Dr.
Netter. For this exciting second edition, we also owe our
gratitude to the Authors, Editors, Advisors, and Artists
whose relentless efforts were instrumental in adapting
these timeless works into reliable references for today’s
clinicians in training and in practice. From all of us with
the Netter Publishing Team at Elsevier, we thank you.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS v

ABOUT THE EDITORS

James C. Reynolds, MD, Editor, is professor of Physicians) and served in this role from 1999 to 2007. Peter J. Ward, PhD, Senior Associate Editor, was
medicine and the June F. Klinghoffer Distinguished From 2006 to 2008 he served as president of the medical born in Denver but grew up primarily in Casper,
Chair of the department of medicine at Drexel Univer- staff at Hahnemann University Hospital and was a Wyoming, graduating from Kelly Walsh High School
sity College of Medicine in Philadelphia. member of the board of directors of the hospital. He in 1992. He attended Carnegie Mellon University in
became interim chair of medicine in 2002. In 2005 he Pittsburgh and graduated with a bachelor of science
Dr. Reynolds, a native of Florida, graduated from was named the June F. Klinghoffer Distinguished Chair degree in biology (genetics, biochemistry, molecular
Florida State University and received his medical of the department of medicine. As Chair he has led the biology) with a minor in chemistry in 1996. He first
degree from the University of Florida, where he was department to a fivefold increase in clinical billing while encountered gross anatomy, histology, embryology, and
president of his class and received several honors, doubling faculty size and extramural research income. neuroanatomy at the College of Veterinary Medicine in
including admission to Alpha Omega Alpha as a junior, The department continues to receive accolades for 1998. Having found a course of study that engrossed
the John B. Gorrie Award as the student with best its support of exceptional quality and transplantation him, he matriculated through these courses at Purdue
promise for outstanding future performance, as well as outcomes and for the national recognition of several College of Veterinary Medicine, as well as at the branch
research awards. He completed his residency at Cornell divisions. campus of the Indiana University School of Medicine.
University at New York Hospital and Memorial Sloan Dr. Ward completed a master’s degree in Dr. Kevin
Kettering Cancer Center. He then completed a 3-year Dr. Reynolds is a member of the editorial board of Hannon’s muscle research laboratory and then began a
fellowship at the Hospital of the University of Digestive Diseases and Sciences and is a reviewer for many doctorate program in anatomy education under Dr.
Pennsylvania. He joined the faculty at the University of other journals. He has published over 100 manuscripts James Walker. He completed his thesis work in 2005—
Pennsylvania, where he became program director and in peer-reviewed journals and has coedited five books. strategies to improve student achievement and recall of
associate chief of the division. He remained funded by He has received numerous honors including Phi Beta medical anatomy—a qualitative and quantitative study.
the National Institutes of Health (NIH) and other Kappa, AOA, and “Physician of the Year” in 1995 by
national organizations for his research into the effect of the Greater Pittsburgh Chapter of the Crohn’s and In July 2005 Dr. Ward joined the faculty of the West
neuropeptides on gastrointestinal motility. In 1990 he Colitis Foundation of America, and has been recog- Virginia School of Osteopathic Medicine (WVSOM) in
became chief of the division of gastroenterology, hepa- nized as the most outstanding gastroenterologist in Lewisburg, West Virginia. He has taught gross anatomy,
tology, and nutrition at the University of Pittsburgh, Pittsburgh on two separate occasions by Pittsburgh embryology, neuroscience, histology, radiography, and
where he was a tenured associate professor of medicine Magazine. He has also been named among Philadel- the history of medicine. During this time he has also
and cell biology. He was co-director of the Centers phia’s “Top Docs” 10 times by Philadelphia Magazine. been director of the WVSOM plastination facility,
for Digestive Health and an associate professor of med- He has received teaching awards in both basic and clini- coordinator of the graduate teaching fellows, chair of
icine and cell biology. In 1996 he became professor cal sciences from the University of Pennsylvania and the curriculum committee, creator and director of a
of medicine with tenure and chief of the division of Drexel. clinical anatomy intensive elective course, host of many
gastroenterology and hepatology at MCP Hahnemann anatomy-centered events between WVSOM and the
University, now the Drexel University College of Med- Dr. Reynolds is board certified in internal medicine Japan College of Osteopathy and the Atlas College of
icine. He held this position and that of program direc- and gastroenterology and hepatology by the American Osteopathy. Dr. Ward has also served on the council of
tor from 1996 to 2008. In those 12 years he held Boards of Internal Medicine. His primary clinical inter- the American Association of Clinical Anatomists and
numerous leadership roles in the hospital and college ests are in the early detection and prevention of cancer, several of the special interest groups of the same orga-
of medicine. He was elected vice-president of the complications of gastroesophageal reflux, and gastroin- nization. He is also a member of the American Associa-
university physicians practice plan (Drexel University testinal motility disorders. tion of Anatomists, American Association for the
History of Medicine, and the American Association
of Veterinary Anatomists. His research continues to
explore how medical students learn effectively, with
particular emphasis on anatomy. In conjunction with
Bone Clones, Inc., Dr. Ward has been producing a
series of tactile models that mimic the feel of anatomical
structures when intact and when ruptured during the
physical examination. He enjoys exploring the use of
video and other media as a supplementary resource in
medical education. These videos are available to view
at Clinical Anatomy Explained! on YouTube.

vi THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

About the Editors

David A. Katzka, MD, Associate Editor, is a pro- Henry P. Parkman, MD, Associate Editor, Michele A. Young, MD, Associate Editor, is a
fessor of medicine and head of the esophageal received his bachelor’s degree from Harvard Uni- clinical assistant professor of medicine and the
interest group at the Mayo Clinic, Rochester, versity and his medical degree from Case Western director of the GI fellowship program at the University
Minnesota. He attended the Mount Sinai School of Reserve University. He completed residency training at of Arizona School of Medicine–Phoenix and the associ-
Medicine, where he also completed his internship and Johns Hopkins Hospital and a gastroenterology fellow- ate chief of medicine in gastroenterology at Phoenix VA
residency followed by fellowship at the Hospital of the ship at the Hospital of the University of Pennsylvania Medical Center. Before entering medical school at
University of Pennsylvania. During his 27 years in under the direction of Dr. Sidney Cohen and Dr. James the State University of New York–Stony Brook, she
Philadelphia he rose to the level of professor of medi- Reynolds, along with GI research training at the Mayo received a master of science degree from the University
cine at the University of Pennsylvania. He spent years Clinic. Since joining the faculty of Temple University of Wisconsin–Madison in communication disorders.
studying esophageal diseases, first with Dr. James School of Medicine in 1990, Dr. Parkman has been Dr. Young then worked for several years at Burke Reha-
Reynolds and Sidney Cohen and then Dr. Donald O. actively involved in studying GI motility at both the bilitation Center in White Plains, New York, as a
Castell. Included among his awards are the Louis basic science and clinical levels. His clinical focus has speech pathologist. She later enrolled in Columbia
Duhring Award for the Outstanding Specialist at the been on treating patients with GI motility disorders, University School of general studies in the initial
University of Pennsylvania and the Distinguished Cli- primarily gastroparesis. Through his research and pursuit of her medical degree. She completed her
nician Award by the American Gastroenterological clinical endeavors, he has developed a number of internship, residency, and fellowship at the University
Association. He has published over 200 peer-reviewed collaborations with colleagues in gastroenterology, of Pittsburgh Hospitals. Dr. Young joined the staff as
articles, chapters, and editorials with research interest nuclear medicine, surgery, pathology, physiology, and chief of gastrointestinal motility at the Phoenix VA
in eosinophilic esophagitis, esophageal motor disor- the school of pharmacy. Medical Center and was on the faculty at the University
ders, Barrett’s esophagus, and gastroesophageal reflux of Arizona School of Medicine–Tucson. She later rose
disease. Dr. Parkman is currently a funded member of the to associate chief of medicine in gastroenterology at the
NIH Gastroparesis Clinical Research Consortium, Phoenix VA Medical Center. Dr. Young joined the
established by the National Institute of Diabetes and faculty of the University of Arizona School of Medicine–
Digestive and Kidney Diseases (NIDDK) to enhance Phoenix as clinical assistant professor of medicine and
the understanding of gastroparesis. This research has program director of the gastroenterology fellowship.
better defined the syndromes of diabetic and idiopathic
gastroparesis, and the Consortium is conducting clini-
cal trials to improve the treatment of patients with
refractory symptoms of nausea and vomiting.

Dr. Parkman is in charge of Temple’s GI motility
laboratory, which assesses GI motility dysfunction in
patients. The clinical lab has developed expertise in a
comprehensive array of GI motility tests for clinical
evaluation of patients, including specialized tests of
esophageal and gastric motility. Temple is a referral
center for evaluation and treatment of GI motility
disorders.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS vii

PREFACE

The opportunity to continue to promote the extraor- complexity and integrated beauty of this fascinating physician from Temple University. Dr. Parkman brings
dinary educational value of the exquisite art of Dr. organ system. The classic images Dr. Netter drew were a special new focus on the neurophysiology and electri-
Frank Netter in a state-of-the-art update of this classic preserved whenever possible and altered only as neces- cal physiology of normal gastric function and disease.
series has been an honor for me and my esteemed asso- sary. Dozens of modern radiographic and endoscopic
ciate editors. Netter’s images have brought insightful images have been added to all sections in all volumes. I review common anatomic, physiologic, and clinical
value to students for over 6 decades and have now been The first section in both Parts I and II summarizes aspects of intestinal disorders in Section 1 of Part II.
updated and enhanced to benefit future generations of shared aspects of the digestive system. Each subsequent In Section 2, Dr. Missale Solomon offers a beautifully
students. This updated edition of Digestive System has section is dedicated to a specific organ and reviews written treatment of normal and abnormal disorders of
been rewritten and renewed to include cutting-edge normal anatomy and physiology, pathology, pathophys- the primary digestive organ, the small intestine. In
science and state-of-the-art endoscopic, pathologic, and iology, and disease presentation and treatment. Section 3, one of modern gastroenterology’s eminent
radiographic images, along with Netter’s ageless draw- educators and Dean at the University of Connecticut,
ings and images that provide insights that foster stu- Each section has been written by authors who were Suzi Rose, MD, discusses the colon.
dents’ and practitioners’ understanding of the anatomy, chosen for their dedication to teaching the fascinating
physiology, and pathophysiology of all eight regions aspects of the digestive system. I had the honor of Part III reviews the normal physiology and patho-
that make up the fascinating and complex digestive choosing incredibly distinguished associate editors with physiology of the liver, biliary tract, and pancreas.
system. whom I have had the pleasure of working throughout Grace Su, MD, a distinguished clinician and scientist
my career. In each case they have published expertise from the University of Michigan, has exquisitely
Frank Netter, MD, described by the Saturday Evening in their respective organ system and have demonstrated updated the section on the liver in a way that will bring
Post as the “Michelangelo of Medicine,” continues to be their commitment to and skill in medical education. great insights into this, the largest solid organ in the
an icon in medical education. The insightful imagery Their knowledge and insights bring updated scientific body. John Martin, MD, another premier physician
of his medical illustrations provides value for students understanding of disease mechanisms and current treat- from the Mayo Clinic, provides wonderful modern
at all levels of experience who seek insights into the ments that will convey understanding of the largest and images of the biliary tract in Section 2, as well as
structure and function of digestion in ways that few most complex organ system that is unparalleled by descriptions of its many associated disorders. Section 3,
other texts have in the history of medical education. His other texts. In each section, Dr. Peter Ward updated on pancreatic function and disease, is written by one of
vision for these texts—integrating factual information each of the subsections on normal anatomy and physiol- the world’s premiere scientists and clinicians on pancre-
with visual aids—provides unparalleled insights. While ogy. He has worked hard to preserve the original pic- atology, Dr. David Whitcomb, chief of gastroenterol-
born at the onset of the twentieth century, his back- tures of Dr. Netter while ensuring the accuracy of the ogy and hepatology at the University of Pittsburgh.
ground mimics many modern medical students— text based on current terminology and science.
beginning his education in the arts before becoming a I would like to express my gratitude for the talented
scientist. By following his mother’s wishes to move In Part I of this three-part set I sought to provide and dedicated contributors to this wonderful update.
beyond art and into medicine, Frank Netter used his insights and an overview of the upper digestive tract. First and foremost, thanks must be given to Dr. Netter
passion and brush to communicate the science and the Michele Young, MD, associate chief of gastroenterology posthumously for providing the initial version of this
art of medicine in unparalleled ways. In distinction at the University of Arizona’s Veterans Administrative text and its wonderful illustrations. I especially want to
to anatomy texts that offer images of structure only, Hospital in Phoenix, has written the first organ-focused thank the associate editors and other contributing
Netter’s paintings also brought incredible insights into chapter on the complex anatomy, physiology, and authors. I also want to thank the amazing artists
the pathophysiology of disease. Just as important, in pathophysiology of pharyngeal and upper esophageal who work with the publishers, Jim Perkins, Tiffany
ways unsurpassed by any other text, he and his dedi- functions. New insights into imaging and physiologic DaVanzo, Kristen Wienandt Marzejon, and especially
cated disciples have illustrated how patients are affected understanding of the complexities of swallowing are Dr. Machado, for their talents and commitment to
by the suffering caused by disease. In all three of these provided. David A. Katzka, MD, distinguished profes- preserving the magnificent style and imagery of Dr.
revised parts of Digestive System, new artists, committed sor of medicine at the Mayo Clinic, revised the section Netter’s drawing. I want to thank my editors at Elsevier,
to the style and value of Dr. Netter’s illustrations and on the esophagus, and is clearly one of the world’s Marybeth Thiel and Elyse O’Grady, for their expertise,
led by Carlos Machado, MD, have modernized both the authorities on the topic. New insights into diseases patience , and support. Finally, I want to thank my
science and the art of his illustrations in all aspects of that are common today but were not known at the loving wife for more than 4 decades of unwavering
the digestive system. time of the first edition, including Barrett’s esophagus support of my efforts to make contributions to the field
and eosinophilic esophagus, are beautifully illustrated of gastroenterology, which never ceases to fascinate and
This update of the digestive system’s anatomy and and discussed. Part I closes with a section by Henry challenge me.
disease has taken a new approach to communicate the Parkman, MD, a renowned gastric physiologist and
James C. Reynolds, MD

viii THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

ADVISORY BOARD

Julio C. Bai, MD Juan Andrés de Paula, MD David Rubin, MD
Chair of Gastroenterology Chief of the Intestinal Diseases Section Joseph B. Kirsner Professor of Medicine
University of El Salvador Gastrointestinal Division Section Chief, Gastroenterology, Hepatology,
Hospital de Gastroenterología Dr. Carlos Bonorino Hospital Italiano de Buenos Aires
Associate Professor of Medicine and Physiology and Nutrition
Udaondo University Institute Hospital Italiano de Buenos Aires Co-Director, Digestive Diseases Center
Buenos Aires, Argentina Buenos Aires, Argentina University of Chicago Medicine and Duchossois
Brian P. Bosworth, MD Janusz A. Jankowski, MD, PhD
Associate Professor of Medicine Consultant Physician Center for Advanced Medicine
Director, Gastroenterology Fellowship Program University Hospitals of Coventry and Warwickshire Chicago, Illinois
Weill Cornell Medical College Honorary Professor Peter D. Siersema, MD, PhD
New York Presbyterian Hospital Warwick Medical School, University of Warwick Professor of Gastroenterology
New York, New York Coventry, United Kingdom Head, Department of Gastroenterology
Marcia Cruz-Correa, MD, PhD
Associate Professor of Medicine and Biochemistry and Hepatology
University of Puerto Rico University Medical Center Utrecht
Director, Gastrointestinal Oncology Program Utrecht, The Netherlands
University of Puerto Rico Cancer Center
San Juan, Puerto Rico

CONTRIBUTORS

EDITOR Michele A. Young, MD Neilanjan Nandi, MD
James C. Reynolds, MD Professor of Medicine Assistant Professor of Medicine
June F. Klinghoffer Distinguished Professor Associate Chief of Gastroenterology Associate Program Director
Phoenix VA Health Care System Division of Gastroenterology
and Chair Phoenix, Arizona Drexel University College of Medicine
Department of Medicine Plates 2-31–2-72 Hahnemann University Hospital
Drexel University College of Medicine Philadelphia, Pennsylvania
Philadelphia, Pennsylvania CONTRIBUTORS Plate 1-54
Plates 1-42–1-53, 1-55–1-66 Asyia Ahmad, MD Ron Schey, MD, FACG
Associate Professor of Medicine Associate Professor of Medicine
SENIOR ASSOCIATE EDITOR Chief of Gastroenterology Associate Director, Neurogastroenterology and
Peter J. Ward, PhD Program Director in Gastroenterology and
Associate Professor of Anatomy Esophageal Disorders Program
Department of Biomedical Sciences Hepatology Section of Gastroenterology
West Virginia School of Osteopathic Medicine Drexel University College of Medicine Temple University Physicians
Lewisburg, West Virginia Philadelphia, Pennsylvania Philadelphia, Pennsylvania
Plates 1-1–1-41, 2-1–2-30, 3-1–3-14, 4-1–4-19 Plates 4-31, 4-38, 4-46, 4-69, 4-70 Plates 4-21, 4-22, 4-36, 4-37, 4-68
Rosemarie Arena, MD Missale Solomon, MD
ASSOCIATE EDITORS Gastroenterology Fellow Assistant Professor of Medicine
David A. Katzka, MD Drexel University College of Medicine Director, Nutrition and Small Bowel Disorders
Professor of Medicine Philadelphia, Pennsylvania Drexel University College of Medicine
Mayo Clinic Plates 4-32, 4-39, 4-58, 4-59 Philadelphia, Pennsylvania
Rochester, Minnesota James N. Kimbaris, MD Plate 4-27
Plates 3-15–3-38 Fellow in Gastroenterology
Henry P. Parkman, MD Temple University Hospital
Professor of Medicine Philadelphia, Pennsylvania
Director, GI Motility Laboratory Plates 4-36, 4-68
Temple University School of Medicine
Philadelphia, Pennsylvania
Plates 4-20, 4-23–4-26, 4-28–4-30, 4-33–4-35,

4-40–4-45, 4-47–4-57, 4-60–4-67

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS xi

SECTION 1 

OVERVIEW OF UPPER
DIGESTIVE TRACT

Plate 1-1  Upper Digestive Tract: PART I

Development of DEVELOPMENT OF GASTROINTESTINAL TRACT AT 14 AND 16 DAYS
Gastrointestinal Tract
A. 14 days Neural plate of embryonic disc B. Section of A Neural
Amnion Amniotic cavity groove
Amnion
Body stalk Amniotic Somite
cavity
Lateral
Extra- plate of
embryonic meso-
Allantois cavity derm

Yolk sac

Plane of section

Yolk sac

We will take a very short tour of early development Chorion
prior to the trilaminar embryo stage, at which time we Chorionic villus
will follow the development of the gastrointestinal tract
in detail. Thereafter, for each region of the gastrointes- Extraembryonic coelom
tinal tract, we will begin with a short summary of the
specific embryology relevant to the structures in that C. 16 days Amniotic cavity D. Section of C Neural groove
region. The single-celled zygote begins dividing roughly Amnion Tail fold Somite
30 hours after an oocyte is fertilized by a spermatozoa. Amnion
It continues dividing without growing substantially Head fold Amniotic cavity
until it reaches the 16-cell stage and is then referred to
as a morula. The morula consists of an outer cell mass Foregut Hindgut Intraembryonic Somatic
surrounding an inner cell mass, which will become the cavity mesoderm
placenta and the embryo, respectively. For the purpose of Cardiac area Visceral
this section we will focus on the inner cell mass as it Connecting Extra- mesoderm
morphs to create the body and the organs within. Extraembryonic stalk embryonic Midgut
cavity cavity
As the zona pellucida (a protective covering of the
oocyte and later the zygote) gradually disappears, fluid Midgut Allantois
penetrates the morula and creates a space between the Yolk sac
inner and outer cell masses. The inner cell mass remains KEY Yolk sac
in contact with the outer cell mass in one section, which Endoderm
will eventually form the connecting stalk and umbilical Mesoderm Plane of section
cord, connecting the embryo to the placenta. The fluid- Ectoderm
filled space between the two cell masses is called the
blastocyst cavity and at this time, roughly 4 days after except for a connecting stalk that will eventually become the prechordal plate, a structure that marks the cranial/
fertilization, the entire structure is called a blastocyst. the umbilical cord. As the 13th and 14th days proceed, superior pole of the developing embryo. Opposite the
Normally, the blastocyst implants into the uterine the primary yolk sac is compressed and pinched in two prechordal plate, epiblast cells begin to proliferate near
lining starting on the sixth day and further development by the expanding extraembryonic cavity. One small the embryo’s caudal/inferior pole. These cells will form
occurs within. remnant moves away from the bilaminar disc while the a structure called the primitive streak. This will eventu-
larger piece remains in contact with the hypoblast and ally result in the process of gastrulation, during which
On the eighth day, another fluid-filled space forms is now called the secondary yolk sac. The secondary yolk the bilaminar disc is replaced by a trilaminar disc. Gas-
between the inner cell mass and the rest of the blasto- sac is lined by cells that are derived from the hypoblast. trulation begins on the 15th day and results in the
cyst. This is the amniotic cavity; despite its small initial In one region, these hypoblast cells enlarge and form replacement of the epiblast and hypoblast layers by
size, it will eventually enlarge to surround the entire
embryo. The portion of the inner cell mass that is in
contact with the amniotic cavity, and amniotic fluid
therein, is called the epiblast, and the portion that is in
contact with the blastocyst cavity is called the hypoblast.
The epiblast cells are tall columnar cells, and the
smaller hypoblast cells appear cuboidal or squamous
(flat). The epiblast and hypoblast layers constitute the
bilaminar disc. By the ninth day, when the blastocyst has
fully implanted into the uterus, the blastocyst cavity is
referred to as the primary yolk sac. Cells that separate
the primary yolk sac, bilaminar disc, and amniotic cavity
from the developing placenta (cytotrophoblast and syn-
cytiotrophoblast) form the extraembryonic mesoderm.

By the 12th day, fluid-filled gaps within the extraem-
bryonic mesoderm converge and form yet another
space, the extraembryonic cavity, which will compress the
primary yolk sac before physically separating it and the
bilaminar disc from the rest of the developing placenta

2 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-2  Overview of Upper Digestive Tract

DEVELOPMENT OF GASTROINTESTINAL TRACT AT 18 DAYS AND 1 MONTH

E. 18 days F. Section of E Neural tube
Midgut Plane of section F Neural crest
Dorsal mesentery Visceral mesoderm
Foregut Plane of section G Intraembryonic Somatic mesoderm
Oropharyngeal Hindgut cavity
membrane Body fold Body fold
Stomodeum Cut edge Cut edge
of amnion of amnion
Proctodeum Extraembryonic
Cut edge cavity Midgut
of amnion
Vitelline duct
Development of Cut edge Connecting
Gastrointestinal Tract of amnion stalk Yolk sac
Allantois
(Continued) Cardiac
area

Yolk sac

three new germ cell layers, collectively called the G. Section of E Neural tube H. 1 month Plane of section I (anterior)
trilaminar embryo. It consists of the embryonic ectoderm, Neural crest Stomach
embryonic mesoderm, and embryonic endoderm. As these Visceral Dorsal pancreas
layers are referred to hereafter, the word “embryonic” Dorsal mesoderm Esophagus Hepatic diverticulum
will be dropped. mesentery
Somatic Lung bud Midgut
To form the trilaminar disc, the primary streak Body fold mesoderm Thyroid Plane of section
extends from the caudal end of the epiblast toward the gland I (posterior) Hindgut
prechordal plate but does not quite reach it. As it Midgut Pharynx Proctodeum
extends cranially, replicating epiblast cells involute into Body fold Cut edge
it, invading the space between the epiblast and hypo- of amnion
blast, creating a fissure called the primitive groove. This
process occurs along the entirety of the primitive streak, Cut edge Cut edge
but there are some important features that occur at its of amnion Left divisionof amnion
cranial end, at an area called the primitive node. The Right division of abdominal
epiblast cells that migrate through the primitive node of abdominal coelom
migrate between the epiblast and hypoblast layers, coelom Stomodeum
moving directly toward the prechordal plate, forming a Ventral mesentery Connecting
signaling structure called the notochordal process, an Cardiac stalk
important structure in directing further development of area Allantois
the three germ cell layers. As gastrulation proceeds, the Vitelline duct
hypoblast is entirely replaced by cells that migrate Cut edge of amnion Yolk sac
through the primitive streak and settle in contact with
the secondary yolk sac. This layer is the endoderm and I. Sections of H Neural tube Neural tube
will produce many of the body’s glands as well as the Neural crest
cells that line the respiratory, urogenital, and gastroin- Neural crest Visceral
testinal tracts. The cells of the former epiblast are now Dorsal mesentery peritoneum
referred to as ectoderm; this layer will produce the Dorsal
epidermis, central nervous system, peripheral ganglia, Duodenum Dorsal pancreas mesentery Parietal
and other cells of neural crest derivation. Between the Abdominal cavity peritoneum
endoderm and ectoderm is the mesoderm, a layer that Visceral Body fold
will produce the kidneys and gonads, as well as the peritoneum Midgut Cut edge
vascular, muscular, and connective tissue structures of Persisting edges of amnion
the body. At this stage, we could choose to follow the Abdominal of ventral mesentery
development of any of the organ systems, but for the cavity Posterior
purpose of this volume we will focus on the develop-
ment of the gastrointestinal system. Other systems will Parietal
be mentioned in a more cursory manner when their peritoneum
development affects the gastrointestinal system.
Body fold
The central region of the ectoderm pinches together
to invade the mesoderm and form the midline neural Ventral mesentery Liver Ventral mesentery Cut edge
groove on the 14th day of development. As development (falciform ligament) Anterior (lesser omentum) of amnion
proceeds from the 16th to 18th day, the neural groove
pinches together and invades the mesoderm as the found to the immediate left and right of the neural tube wall that contains the contents of the peritoneal cavity
neural tube, which differentiates to form the spinal cord, and will form somites, which in turn form the axial skel- but it also forms the smooth muscle and connective
brainstem, and cerebral cortex. After the neural tube eton, musculature, and dermis. Just lateral to the par- tissues that surround and support the gastrointestinal
has detached from the ectoderm, other ectodermal axial mesoderm is the intermediate mesoderm, which tract. It also creates the mesenteries that connect the
cells, called the neural crest cells, migrate into the meso- differentiates into gonads and precursors of the kidneys. digestive organs to the anterior and posterior abdomi-
derm. These cells migrate throughout the developing Lateral to the intermediate mesoderm is the lateral plate nal wall. As mentioned already, the endoderm forms the
mesoderm to form the sympathetic chain ganglia, mesoderm, which contributes to the body wall, limbs, lining of the gastrointestinal tract and several of the
ganglia of the cranial nerves, and postsynaptic parasym- and connective tissue structures that anchor the organs organs that develop from it. We will now describe how
pathetic ganglia, among others. The mesoderm also within the body cavities. In the case of the digestive the trilaminar embryo morphs to create the abdominal
undergoes several changes: the paraxial mesoderm is system, the lateral plate mesoderm forms the abdominal cavity and organs within.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 3

Plate 1-3  Upper Digestive Tract: PART I

DEVELOPMENT OF GASTROINTESTINAL TRACT AT 5 WEEKS, 6 WEEKS, AND 2 MONTHS

Developing right pleuro- Arrow passing through right pleural canal
peritoneal membrane from abdominal celom to pericardial celom

Ventral mesentery Esophagus
(lesser omentum)
Transverse septum Stomach J. 5 weeks
Gallbladder Spleen
Liver (cut surface)
Dorsal mesogastrium

Celiac trunk

Dorsal pancreas

Ventral mesentery Common bile duct
(falciform ligament) Mesoduodenum
Vitelline duct Duodenum
Allantoic Ventral pancreas
stalk Superior mesenteric artery

Dorsal mesentery of midgut

Umbilical cord Inferior mesenteric artery

Proctodeum Mesocolon of hindgut

Cloacal membrane Cloaca Allantois Transverse septum Esophagus
Stomach rotating
Liver (cut surface) Spleen

K. 6 weeks Lesser omentum Arrow passing from
Falciform ligament main peritoneal cavity
Development of into omental bursa
Gastrointestinal Tract Gallbladder Dorsal mesogastrium
bulging to left
(Continued) Proximal limb of primary gut loop

The lateral plate mesoderm is continuous on its Vitelline duct
lateral edge with the extraembryonic mesoderm that sur-
rounds the developing embryo. It is sandwiched by the Allantoic stalk Dorsal pancreas
ectoderm and amniotic cavity dorsally; the endoderm within mesoduodenum
and secondary yolk sac are located ventral to it. At 14 Extraembryonic celom
days of development, the lateral plate mesoderm con- within umbilical cord Ventral pancreas passing
stitutes a single mesodermal region, but shortly there- Cecum on distal limb of primary gut loop into mesoduodenum
after, gaps form within it that create a continuous, Superior mesenteric artery
horseshoe-shaped space that extends from right to left, Umbilical ring within dorsal mesentery
going around the cranial end of the embryo. This space
is the intraembryonic cavity; as it enlarges, it becomes Liver (cut surface) Urorectal fold Urinary bladder Mesocolon of hindgut
continuous with the extraembryonic cavity and it splits
the lateral plate mesoderm into two layers. The parietal Gallbladder
(somatic) layer of lateral plate mesoderm is the more supe-
rior of the two and is in direct contact with the ecto- Falciform ligament
derm and amniotic cavity. The more inferior layer is
the visceral (splanchnic) layer of lateral plate mesoderm and Cecum passing to right Diaphragm
is in contact with the underlying endoderm and second- above coils of small Greater curvature of stomach
ary yolk sac. This separation is complete but not really intestine rotated 90° to left
dramatic by the 16th day. However, as this space
enlarges, it pushes the visceral layer and endoderm Yolk stalk Spleen within
medially, creating a notable separation by the 18th day. dorsal mesogastrium bulging to left
The visceral layers of lateral plate mesoderm and endo- Allantoic stalk to form omental bursa
derm on each side grow closer to each other, pinching
the endoderm on the left and right, creating a tube that Umbilical cord Pancreas within mesoduodenum
is separate from the rest of the secondary yolk sac. As
this proceeds, the yolk sac stretches away from the Genital tubercle Superior mesenteric artery
developing gut tube and remains connected to it via the Urogenital sinus within dorsal mesentery
vitelline duct at the midgut, which will form the small Anus
intestine and part of the large intestine. Aside from its Ureter Mesocolon L. 2 months
connection to the vitelline duct and secondary yolk sac, Rectum Colon
the rest of the endoderm and accompanying visceral
lateral plate mesoderm fuse to form a complete tube Urinary bladder
that stretches from the oropharyngeal membrane (devel-
oping mouth) to the cloacal membrane (eventual anus and Urorectal septum
urogenital openings). This tube is the early gastrointes-
tinal tract, and it will give rise to all the organs of digestion as well as the respiratory and urogenital tracts. extension of the primary yolk sac, extends off of the
From cranial to caudal, it is divided into the foregut developing hindgut, and as development proceeds, it
(esophagus, stomach, proximal duodenum, liver, spleen, extends into the connecting stalk, cranial to the cloacal
pancreas), midgut (distal duodenum, jejunum, ileum, membrane. It contributes to the wall of the urinary
vermiform appendix, cecum, ascending and transverse bladder, but that is not our focus at this time. Eventually
colon), and hindgut (descending colon, sigmoid colon, both the vitelline duct and allantois will extend along-
and rectum). In addition to the vitelline duct, another side each other into the umbilical cord, and aberrations
pouch of endoderm stretches away from the developing of each structure are associated with malformations of
gut tube, the allantois. This pouch, originally a caudal the midgut and urinary bladder, respectively.

4 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-4  Overview of Upper Digestive Tract

DEVELOPMENT OF GASTROINTESTINAL TRACT AT 10 WEEKS AND 4 TO 5 MONTHS; DIAPHRAGM AT 9 WEEKS

Cecum M. 11 weeks
(continuing to
rotate after Descending colon against dorsal abdominal wall
returning last Coiled small intestine
to abdominal
cavity from
umbilical cord)

Umbilical cord
Disappearing yolk stalk

N. 4 to 5 months

Transverse colon Left colic
Duodenum flexure

Development of Right colic flexure Ileum Rectum Root of
Gastrointestinal Tract Root of transverse Cut edge Anus transverse
mesocolon (right half) of mesentery mesocolon
(Continued) Ascending colon (left half)
Triangular fusion of Aorta
While the gut tube is forming from the endoderm ascending mesocolon Duodenojejunal
and visceral lateral plate mesoderm, a similar process is to dorsal wall flexure
occurring with the ectoderm and parietal lateral plate Root of mesentery Descending
mesoderm, so that a left and right lateral fold will form of small intestine colon
and fuse anteriorly to become the body wall. The left Cecum in final Quadrangular
and right lateral folds first extend toward the yolk position of rotation fusion of
sac and then turn medially. As this happens, these layers Vermiform appendix descending
pull the amniotic sac, which had previously covered a mesocolon to
small area, to surround the entire developing embryo. O. Diaphragm 9 weeks dorsal wall
Cross sections of the developing embryo at 18 days will Dorsal mesentery
appear remarkably different, depending upon whether of esophagus Root of sigmoid
or not the cross section includes the secondary yolk sac (mediastinum) mesocolon
and vitelline duct. A cross section that includes the yolk
sac will show an incompletely fused gut tube at the Contribution Sigmoid colon
midgut, with the vitelline duct leading away from, and from right
opening into, a ballooned yolk sac. The lateral folds pleuroperitoneal Contribution
have not yet migrated anteriorly enough to form a com- membrane from left
plete body wall. However, a cross section in a more pleuroperitoneal
posterior plane will exclude the yolk sac and show a Inferior membrane
fused anterior body wall surrounding a circular gut vena cava Esophagus
tube. The gut tube remains anchored to the anterior
body wall by the ventral mesentery, which will largely Contribution from
disappear, and the dorsal mesentery, which will remain transverse septum
and transmit the vessels and nerves that connect the gut
tube to the rest of the body. The gut tube, with its sur- sum narrows the peritoneal cavity considerably, leaving creating the diaphragm by the ninth week. Later, the
rounding visceral layer of lateral plate mesoderm, sepa- two small openings between the pericardial cavity in the musculature of the diaphragm develops as a secondary
rates the right and left peritoneal cavities, “descendants” thorax and the peritoneal cavity in the abdomen. These ingrowth from the body wall. The phrenic innervation
of the intraembryonic coelom to either side. When the are the pericardioperitoneal canals and they are normally from the cervical spinal cord to the diaphragm origi-
ventral mesentery disappears, there will be a single peri- closed as the diaphragm receives a left and right pleuro- nates when the transverse septum first develops at
toneal cavity. By this time, the amniotic cavity almost peritoneal membrane from the body wall. Contributions the cervical level of the embryo. As the septum shifts
entirely covers the developing embryo, with only a from the dorsal mesentery of the esophagus and muscle to a low thoracic level, the phrenic nerves elongate.
narrow span of mesoderm separating the right and left from the body wall assist in closing these canals and The commonest developmental abnormality of the
lateral folds.

Before 1 month of development has passed, the heart
has descended into the thoracic region, bringing along
a mesodermal structure, the septum transversum, which
will contribute to the diaphragm. The septum transver-

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 5

Plate 1-5  Upper Digestive Tract: PART I

Development of RELATIONSHIPS OF STOMACH AT 2 MONTHS; SAGITTAL SECTION AT 2 TO 3 MONTHS
Gastrointestinal Tract
2 months
(Continued)
Cut edge of
ventral mesentery
(lesser omentum)

Root of dorsal
mesogastrium

Gallbladder Stomach
Hepatic duct Spleen
Common bile duct
Arrow passing into Jejunum Dorsal mesogastrium
developing growing ventrocaudally
omental bursa (greater omentum)

Original dorsal Dorsal mesentery
pancreatic duct of small intestine
Original ventral
pancreatic duct
Duodenum
rotating and
passing to right

Pancreas within
mesoduodenum

diaphragm is a faulty growth of the left pleuroperito- 2 to 3 months Coronary ligament
neal membrane, resulting in an opening through which Septum transversum Inferior vena cava
abdominal viscera may herniate into the left pleural Bare area of liver Arrow passing into
cavity. Coronary ligament omental bursa
Portion of pancreas within
Caudal to the developing diaphragm is the foregut. Gallbladder dorsal mesogastrium
The ventral and dorsal mesenteries remain in contact Falciform ligament (greater omentum)
with the foregut, but the ventral mesentery disappears Head of pancreas within
along the midgut and hindgut, leaving the developing Stomach mesoduodenum fused
gut tube suspended in the abdominal cavity. From the Umbilical cord to dorsal wall
dorsal aorta, the celiac trunk supplies blood to the Umbilical vein Duodenojejunal
foregut, and its branches will supply all of the foregut Greater junction
organs as they develop. Extensions of the foregut omentum growing Transverse
stretch into the ventral and dorsal mesenteries to create ventrocaudally mesocolon
the hepatic diverticulum and dorsal pancreatic bud, respec- Transverse colon Dorsal mesentery
tively. The hepatic diverticulum will form the liver and Small intestine of small intestine
gallbladder but will also give rise to a ventral pancreatic
bud, which will fuse with the dorsal pancreatic bud to systems initially empty into a common chamber, the totally partitioned the digestive and urogenital systems,
form the entire pancreas. The ventral mesentery cloaca, which is separated from the amniotic cavity by a leaving a urogenital membrane and anal membrane on the
remains in contact with the developing liver, eventually cloacal membrane. The allantois extends from the cranial external surface of the body in the place of the cloacal
forming the falciform ligament. The further develop- end of the cloaca and stretches into the umbilical cord membrane. The inferior mesenteric artery will supply all
ment of this region will be covered in the sections alongside the vitelline duct. Between 4 and 7 weeks, the the hindgut organs. The further development of this
related to the specific foregut organs, the esophagus, mesoderm located between the allantois and the vitel- region will be covered in the sections related to the
stomach, duodenum, liver, gallbladder, and pancreas. line duct/midgut, called the urorectal septum, extends large intestine and anal regions.
caudally and separates the hindgut from the rest of the
During the sixth week the midgut has begun to elon- cloaca, which will hereafter be called the urogenital Although the foregut began as a simple, midline,
gate substantially and runs out of room within the peri- sinus. By the end of 7 weeks, the urorectal septum has tubular structure lined by epithelium derived from
toneal cavity. It moves into the umbilical cord, creating endoderm, it twists, expands, and elongates to create
a physiologic umbilical herniation, which is a normal event
in the development of the gastrointestinal system. The
vitelline duct has narrowed but still connects the midgut
to the secondary yolk sac, and this connection is one of
the reasons that the physiologic herniation occurs,
pulling the midgut into the umbilical cord. The vitel-
line duct will typically disappear roughly 10 weeks into
development as the midgut starts returning to the peri-
toneal cavity. The superior mesenteric artery is derived
from the vitelline artery and supplies all the developing
midgut structures and, eventually, all organs of the
midgut. The further development of this region will be
covered in the sections related to the small and large
intestines.

Development of the hindgut is intimately connected
with the urinary and reproductive systems. All three

6 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-6  Overview of Upper Digestive Tract
SAGITTAL SECTIONS AT 3 TO 4 MONTHS COMPARED WITH ADULT

Development of 3 to 4 months Bare area of liver
Gastrointestinal Tract Diaphragm Coronary ligament

(Continued) Coronary ligament Inferior vena cava
Cut surface
of liver Arrow passing through
epiploic foramen
Falciform ligament Common bile duct
Omental bursa Portion of pancreas within
Umbilical vein dorsal mesogastrium
Umbilical cord (greater omentum)
Duodenojejunal junction
Greater omentum Transverse mesocolon
growing caudally
Transverse colon Mesentery of
small intestine
Small intestine

the adult relationships between each abdominal organ. Adult relationships Bare area of liver
Fusing and expansion of the dorsal mesenteries are key Coronary ligament
in this process. The portion of the foregut that will Diaphragm Caudate lobe of liver
become the stomach first starts to expand in the sagittal Coronary ligament Arrow passing through
plane, ballooning outward on its anterior and posterior Cut surface of liver epiploic foramen
surfaces. However, the expansion of the posterior Common bile duct
surface quickly outpaces the other side and the stomach Gallbladder Body of pancreas
begins to bend. The enlarged expansion of the posterior Lesser omentum Third part of duodenum
side will become the stomach’s greater curvature, and Falciform ligament secondarily covered by
the anterior side will become the lesser curvature. As fusion of ascending
this is happening, the presumptive stomach rotates so Stomach mesocolon to wall
that the posterior side shifts toward the left of the body Ligamentum teres Fusion of dorsal
while the anterior right side shifts to the right. The mesogastrium and
rotation and expansion of the posterior side are what Omental bursa transverse mesocolon
give the stomach its characteristic shape, with the Greater omentum Root of mesentery
esophagus entering just to the right of the fundus and of small intestine
greater curvature, and the outlet of the stomach, the Transverse colon
pyloric region, shifting to the right and slightly superior Fusion of layers of the liver, and posterior to the stomach and lesser
to the greater curvature. This moves the stomach from of greater omentum, which can be subdivided into the hepatogas-
a superior/inferior axis to more of a right/left axis omentum (apron) tric and hepatoduodenal ligaments. Occasionally the
within the abdomen. The inner, circular layer of muscle omental bursa can extend superiorly and posteriorly to
at the terminus of the stomach enlarges significantly to Small intestine the liver as the superior recess of the omental bursa. In its
form the pyloric sphincter. mature form, the omental bursa is isolated from the rest
The pocket thus formed is called the omental bursa. of the abdominal cavity, except for a small opening
The rotation and expansion of the stomach do not Continued rotation and expansion of the greater curva- called the omental foramen located immediately poste-
occur in isolation. The foregut is attached to the pos- ture bring this double-layered “apron” to extend rior to the right edge of the hepatoduodenal ligament.
terior body wall by a dorsal (posterior) mesentery, called inferiorly from the stomach, falling anterior to the
the dorsal mesogastrium, in which the spleen and dorsal transverse colon and small intestine. The motion of the
part of the pancreas will develop. The section of this developing stomach and growth of the liver shift
mesentery between the developing spleen and the the stomach to the left and the liver to the right side of
stomach will become the greater omentum. Anteriorly it the abdomen. This also brings the omental bursa to lie
is connected to the liver, and thereafter, to the anterior anterior to the pancreas, inferior to the inferior surface
body wall by a ventral (anterior) mesentery. The section
of the ventral mesentery that attaches the liver to the
anterior body wall will become the falciform ligament,
and the section between the liver, stomach, and duode-
num will form the lesser omentum. As the stomach’s
posterior surface expands and rotates to the left, the
attached mesentery follows, laying the spleen along the
left side of the abdominal cavity. The dorsal mesentery
between the stomach and spleen expands, folding onto
itself and creating a large pocket between the two folds.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 7

Plate 1-7  Upper Digestive Tract: PART I

Right upper Left upper Right Left
quadrant quadrant lateral rectus plane lateral rectus plane
(RUQ) (LUQ) linea semilunaris linea semilunaris

Right lower Left lower Left
quadrant quadrant midclavicular
(RLQ) (LLQ) Right line
midclavicular
line

Regions of the Abdomen 1
2

For the sake of convenience, the abdomen is tradition- Epigastric 3 Left
ally divided into either four or nine regions. Of these region T12 hypochondrium
two (somewhat artificial) divisions, the more simple one 4
uses two imaginary planes, one passing vertically and Right hypochondrium (hypochondriac
the other horizontally through the umbilicus, dividing (hypochondriac region) 5 L1 region)
the abdomen into four quadrants, the right upper, left Transpyloric plane 6 L2
upper, right lower, and left lower quadrants. Subcostal plane 7 L3 Left flank
Umbilical region 8
A division of the abdomen into nine smaller areas is Right flank (lumbar region) 9 (lumbar
accomplished by the use of two vertical and two hori- 10 region)
zontal planes. The zone above the upper of the two L5
horizontal planes is divided by the two vertical planes Intertubercular plane
into a centrally placed epigastric region (epigastrium), Interspinous plane Left groin
with a right and left hypochondriac region on each side of (inguinal
it. The zone between the two horizontal planes is Right groin (inguinal region) region)
divided into a centrally placed umbilical region, with a Pubis (hypogastric
left and right lumbar region on each side. The zone below region) not confined to any one region. Attention should be
the lower of the two horizontal planes has a centrally called to the fact that, because the diaphragm is the
placed hypogastric region and a right and left inguinal common way of locating the vertical plane on each side upper limit of the abdomen, most of the hypochondriac
region. uses the lateral border of the rectus abdominis muscle (as the name indicates) regions and parts of the epigas-
or the semilunar line, which, if followed inferiorly and tric region are under cover of the ribs. Because these
Different resources list different landmarks as the medially toward the pubic tubercle, brings the entire three regions make up a good portion of the right and
basis for drawing the lines of the nine-region scheme. inguinal canal into the inguinal region. left upper quadrants, these quadrants also extend well
The upper horizontal (superior transverse) line, or up under the ribs.
plane, may be drawn halfway between the superior In attempting to use either quadrants or the smaller-
border of the sternum and the superior border of the sized nine regions in the localization of viscera, one
symphysis pubis. This plane has been considered as finds that a substantial number of individual organs are
passing through the pylorus and has thus been called
the transpyloric plane, which also has been described as
being halfway between the xiphisternal junction and the
umbilicus, and passing through the tip of the ninth
costal cartilage, the fundus of the gallbladder, and the
lower part of the body of the first lumbar vertebra.
Another way of locating the upper horizontal plane is
at the most inferior part of the costal margin (usually
the most caudal part of the 10th costal cartilage). This
plane is called the subcostal plane.

The lower horizontal (inferior transverse) line, or
plane, may be assigned to the levels of the tubercles of
the iliac crests and is called the transtubercular plane; it
usually passes through the lower part of the fifth lumbar
vertebra, or it may be located at the level of the anterior
superior spine of the ilium and called the interspinous
plane. It has also been located at the highest points of
the iliac crests and called the supracristal plane.

The two vertical planes, or lines, one on each side,
may be located halfway between the median plane and
the anterior superior spine of the ilium (or halfway
between the pubic tubercle and the anterior superior
spine of the ilium or the midpoint of the inguinal
ligament; right and left midinguinal planes). The other

8 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-8  Overview of Upper Digestive Tract

Costal 4 Body of
cartilages 5 sternum
6 Xiphoid
Bony Framework of process
Abdominopelvic Cavity

The skeletal framework that serves as the attachment 7 T11
site for the muscles that make up the abdominal and T12
pelvic walls consists of the lower ribs, costal cartilages, 8 12th
five lumbar vertebrae, and bony pelvis. The costal car- L1 rib
tilages of the fifth, sixth, and seventh ribs angle obliquely 9 Sacral L2
upward and medially to join the sternum superior and promontory L3 Transverse processes
lateral to the xiphisternal junction. The terminal Iliac 10 L4 of lumbar vertebrae
portion of each of the 8th, 9th, and 10th costal carti- crest L5
lages tapers to a point and is attached to the lower Iliac tuberosity
border of the costal cartilage above. The 11th and 12th Inner lip
costal cartilages are quite short, with pointed tips, Intermediate Iliac crest
neither of which attaches to the cartilage above it. The zone
lower border of the 10th costal cartilage is commonly Outer lip Wing (ala)
the most inferior part of the caudal margin of the tho- Tuberculum of ilium
racic cage. From the beginning of the 10th costal car-
tilage to the junction of the 7th costal cartilage with the Anterior Sacrum Greater
sternum, a cartilaginous border is formed, which is fre- superior Coccyx sciatic
quently referred to as the “costal arch” (costal margin), iliac spine notch
although this term is perhaps more correctly used to Anterior Inferior pubic ligament Pubic arch Arcuate
refer to the arch formed by the right and left cartilagi- inferior line
nous borders as they are connected by the lower end of iliac spine Ischial
the sternal body from which the variable xiphoid process Iliopubic spine
of the sternum projects. The latter serves as a landmark eminence Lesser
for the level of the body of the 10th (or 11th) thoracic Superior sciatic notch
vertebra. pubic Greater
ramus trochanter
The five lumbar vertebrae present the parts described Obturator of femur
for a typical vertebral body (centrum) and vertebral foramen Pecten
(neural) arch, supporting the two transverse processes, Pubic pubis
the spinous process, and the superior and inferior artic- tubercle (pectineal
ular processes. Inferior line)
pubic Pubic
The bony pelvis is made up of the two hip bones, ramus symphysis
with the sacrum and coccyx wedged between them pos- Lesser trochanter
teriorly. For descriptive purposes, the bony pelvis is of femur
divided by a plane passing through the sacral promon-
tory and the crest of the pubis, into the major (false) Ischial tuberosity
pelvis above the plane and the minor (true) pelvis below
this plane. This plane lies roughly in the inlet of the riorly and posterolaterally, enters into the formation of tuberosity, which projects posteroinferiorly. From the
true pelvis, which is bounded by the sacral promontory, the acetabulum (acetabular portion, sometimes called posterior border of the inner side of the lower part of
crest of the pubis, anterior margin of the ala of the the body) and presents a prominent pecten pubis, or the acetabular portion of the ischium, the ischial spine
sacrum, the arcuate line of the ilium, and the pecten pubis, pectineal line, which is continuous with the arcuate line projects posteromedially between the greater and lesser
all of which could be considered as forming the linea of the ilium. The inferior ramus courses interiorly and sciatic notches. A ramus of the ischium courses anteri-
terminalis. posterolaterally, to join the ramus of the ischium and orly from the lower end of the main portion of the
complete the margins of the obturator foramen. The bone, to become continuous with the inferior ramus of
The hip bone (os coxae or innominate bone) is made main portion of the ischium extends interiorly and pos- the pubis, forming what is often referred to as the ischio-
up of the ilium, pubis, and ischium, which are separate teriorly from the acetabulum, to expand into the ischial pubic ramus.
bones in the young subject but fuse at the acetabulum
in the adult. On the inner surface of the ilium, the
arcuate line indicates the inferior border of the ala of
the ilium, which ends superiorly in the palpable iliac
crest, stretching from the anterior superior spine of the
ilium to the posterior superior iliac spine. The crest also
presents an external (lateral) lip, an internal (medial) lip,
and an intermediate line and thickening on its lateral
aspect a short distance posterior to the anterior superior
spine, which is called the tubercle of the crest. The body
of the pubis joins the pubic bone on the other side, by
means of a fibrocartilaginous lamina, the symphysis pubis.
The upper border of the body, which is thick, rough-
ened, and turned anteroinferiorly, is called the crest,
and at its lateral end is a prominence named the pubic
tubercle. The superior ramus of the pubis, coursing supe-

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 9

Plate 1-9  Upper Digestive Tract: PART I
ANTERIOR ABDOMINAL WALL: SUPERFICIAL DISSECTION

Anterolateral Abdominal Serratus Pectoralis
Wall anterior major
muscle muscle
Before describing the walls of the abdomen, it is neces- Xiphoid
sary to mention different ways in which the word Latissimus process
abdomen is used. In some cases, abdomen is synonymous dorsi Rectus
with abdominopelvic cavity, but in other cases, it is used muscle sheath
in a more specific sense to refer to that portion of the Linea
body cavity between the diaphragm and the pelvis Muscular alba
minor (true pelvis). Abdomen is also used more loosely part Subcutaneous
to refer to a general region of the body. Aponeurotic tissue
part (superficial
For purposes of specificity, it seems advisable to name External fascia) of
that portion of the body cavity below the diaphragm oblique abdomen
the “abdominopelvic cavity” and then to divide this into muscle Camper (fatty)
the abdominal cavity proper and the pelvic cavity (pelvis Anterior layer,
minor), separated from each other by the plane of the superior Scarpa
pelvic inlet (the plane passing through the sacral prom- iliac spine (membranous)
ontory and the pubic crests). It must be remembered, Inguinal layer of
however, that certain structures that are ordinarily ligament subcutaneous
referred to as abdominal structures (some of the coils (Poupart) tissue of
of small intestine, for example) usually hang into the Intercrural abdomen
pelvic cavity, and that the inferior and posteroinferior fibers (turned back)
support of the abdominal viscera is furnished by the Superficial Thoraco-
walls of the pelvic cavity and not by the theoretical inguinal ring epigastric
plane at the pelvic inlet. It is convenient to divide the Fascia lata vein
borders of the abdominopelvic cavity into four general External Attachment
parts—the anterolateral abdominal wall, the posterior spermatic of Scarpa
wall of the abdominal cavity, the diaphragm (superior fascia on layer to
wall or roof of the abdominal and abdominopelvic cavi- spermatic fascia lata
ties), and the bowl of the pelvic cavity, which can be cord Superficial
loosely called the floor of the abdominopelvic cavity. Great circumflex
However, the limits of each boundary are not sharp, saphenous iliac vessels
because we are dealing with curved contours, and vein Superficial
certain arbitrary limits need to be defined for descrip- Superficial epigastric
tive purposes. This has been done in part above and will dorsal vein vessels
be completed as necessary at appropriate places in the of penis Superficial
following descriptions. external
to the underlying layers, except in the area of the pudendal
The anterolateral abdominal wall fills in the gap in umbilicus. vessels
the bony-cartilaginous framework between the costal Fundiform
margin superiorly and the hip bones inferiorly. Follow- The subcutaneous fat is soft, movable, and contains a ligament
ing the curve of the body laterally, several muscles, variable amount of fat, depending mostly on the state Superficial
nerves, vessels, and fascial layers will be encountered. of nutrition of the individual and varying to some extent fascia of
For the present work, the quadratus lumborum muscle in distribution. The thickness of this layer can be penis and
and the structures medial to it will be included with the roughly estimated by picking up a fold, the thickness of scrotum
posterior wall of the abdominal cavity. Owing to its which, minus the double thickness of the skin, would (dartos
muscular components, the anterolateral abdominal wall be about twice the thickness of the layer. The superficial fascia) (cut)
can contract and relax and, thus, help to accommodate Deep (Buck)
the size of the abdominopelvic cavity to changes in fascia of penis
volume of the contained viscera and to control intraab- with deep
dominal pressure. The surgical approach to the abdom- dorsal vein of
inopelvic cavity is commonly made through this wall. penis showing
through
Starting from the outside, the layers of the anterolat-
eral abdominal wall are skin, subcutaneous fat (superfi- fascia, particularly of the part of the wall inferior to the
cial fascia), outer investing layer of deep fascia, the level of the umbilicus, has been classically described as
muscles with their related fasciae, transversalis fascia, having a superficial fatty layer, called the Camper fascia,
extraperitoneal fascia, and parietal peritoneum. Abdom- and a deep membranous layer (to some extent discon-
inal skin is of average thickness (thicker posteriorly tinuous), called the Scarpa fascia. This classical descrip-
than anteriorly and laterally) and rather loosely attached tion is somewhat of a simplification of the actual
situation, in which the layering is not always as clear-cut
as indicated, but it serves as a means of description if
this is kept in mind. The Camper layer is continuous

10 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-10  Overview of Upper Digestive Tract
ANTERIOR ABDOMINAL WALL: INTERMEDIATE DISSECTION

Anterolateral Abdominal Latissimus 6 Pectoralis
Wall (Continued) dorsi muscle major
Serratus 7 muscles
with the fatty layer of surrounding areas, such as the anterior muscle 8 Anterior
superficial fascia of the thigh. The Scarpa layer fuses External 9 layer of
with the fascia lata along a line parallel to and just oblique muscle 10 rectus sheath
inferior to the inguinal ligament. Medial to the pubic (cut away) (cut edges)
tubercle, both layers continue into the urogenital External Linea alba
region. This is significant in relation to the path that intercostal Rectus
extravasated urine takes after injuries to the urethra or muscles abdominis
neck of the bladder. When entering the fasciae in the External oblique muscle
perineal region, this urine and blood may escape supe- aponeurosis External
riorly into the anterolateral abdominal wall. In the (cut edge) oblique
male, the two layers continue into the scrotum and muscle
blend into a single, smooth muscle-containing layer, the Rectus sheath (cut away)
fat being rather abruptly lost as they enter into the Internal Tendinous
formation of the scrotum. Just above the symphysis oblique muscle intersection
pubis a considerable addition of closely set strong bands Anterior superior Internal
to the Scarpa fascia form the fundiform ligament of the iliac spine oblique muscle
penis, which extends down onto the dorsum and sides Inguinal ligament Pyramidalis
of the penis. (Poupart) muscle
Inguinal falx
The outer investing layer of the deep fascia (not Inguinal falx (conjoint
readily distinguished from the muscular fascia on the (conjoint tendon) tendon)
external surface of the external abdominal oblique muscle Cremaster muscle External
and its aponeurosis) is easily demonstrable over the fleshy (lateral origin) oblique
portion of the muscle but is much more difficult to Reflected aponeurosis
separate from the aponeurotic portion of the muscle. inguinal ligament (cut and
This layer is attached to the inguinal ligament and Femoral vein turned down)
blends with the fascia coming out from under this liga- (in femoral sheath) Pectineal
ment to form the fascia lata. It also joins with the fascia Saphenous ligament
on the inner surface of the external oblique at the super- opening (Cooper)
ficial inguinal ring to form the external spermatic fascia. Cremaster muscle Reflected
External to the inferior end of the linea alba, the outer (medial origin) inguinal
investing layer is thickened into the suspensory ligament Cremaster muscles ligament
of the penis, which anchors the penis to the symphysis and cremasteric Lacunar
pubis and the inferior pubic ligament. It is also continu- fascia ligament
ous with the deep fascia investing the penis. (Gimbernat)
Fascia lata
The external abdominal oblique muscle typically arises Pubic tubercle
by eight digitations from the external surfaces of the Great Suspensory
lower eight ribs lateral to the costochondral junction, saphenous vein ligament
the middle group of digitations arising at a greater of penis
distance lateral to the junction than the ones above and (where it partly fuses with the aponeurosis of the inter- Deep (Buck)
below them. The upper five slips interdigitate with the nal oblique) to blend with the one of the opposite side fascia of penis
serratus anterior muscle, and the lower three slips inter- in the midline linea alba, gaining attachment to the External
digitate with the latissimus dorsi muscle. The general xiphoid process at the upper end of the linea alba and spermatic
direction taken by the fibers of this muscle is anteroin- to the pubis at the lower end. The lower margin of the fascia (cut)
ferior from their site of origin, and this leads the fibers aponeurosis is folded backward and slightly upward
from the lower two or three digitations to a fleshy inser- upon itself between the anterior superior iliac spine and Superficial fascia of penis and scrotum (cut)
tion on the anterior half of the outer lip of the crest of the pubic tubercle. The folded edge, together with an
the ilium, this portion of the muscle having a free pos- extremely variable number of fibrous strands running
terior border that forms the anterior side of the lumbar along it, is called the inguinal ligament.
triangle. The muscular portion from the remainder of
the origin becomes the strong aponeurosis of this muscle The nerve supply of the external abdominal oblique
along a line that courses vertically inferiorly through muscle is derived from the ventral rami of the 6th to
about the tip of the ninth costal cartilage to the level of 12th thoracic spinal nerves. The 6th to the 11th are
the anterior superior iliac spine, where it curves rather intercostal nerves, which continue from the intercostal
sharply laterally to course toward this spine. The apo- spaces into the anterolateral abdominal wall to lie in
neurosis passes in front of the rectus abdominis muscle the plane between the internal abdominal oblique and

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 11

Plate 1-11  Upper Digestive Tract: PART I

ANTERIOR ABDOMINAL WALL: DEEP DISSECTION

Anterolateral Abdominal Superior 4 Anterior layer
Wall (Continued) epigastric 5 of rectus sheath
vessels (cut)
transversus abdominis muscles. The 12th thoracic External 6 Linea alba
nerve is the subcostal nerve, and it follows a course oblique
similar to the intercostal nerves above. The iliohypo- muscle Anterior layer
gastric nerve from the anterior ramus of L1 also con- (cut away) of rectus sheath
tributes to the supply. The nerves have a segmental
distribution corresponding to the primitive segmen- Rectus Transversus
tal condition of the muscle, with the 10th thoracic abdominis abdominis
extending toward the umbilicus and the 12th toward a muscle muscle (cut)
point about halfway between the umbilicus and the
symphysis pubis. External 7 Transversalis
oblique 8 fascia (opened
The external abdominal oblique muscle has several aponeurosis on left)
actions in common with the other large muscles of the (cut) 9
anterolateral abdominal wall. These are to (1) support Internal 10 Extraperitoneal
the abdominal viscera and, by compressing them, help oblique fascia (areolar
to expel their contents; (2) depress the thorax in expira- aponeurosis tissue)
tion; (3) flex the spinal column; and (4) assist in rotation (cut) Medial umbilical
of the thorax and pelvis in relation to each other. With Internal ligament
the pelvis fixed in place, contraction of the external oblique (occluded part
oblique of one side produces a rotation that brings the muscle (cut) of umbilical
shoulder of the same side anteriorly. Transversus
abdominis artery)
The internal abdominal oblique muscle, smaller and muscle Inferior
thinner than the external oblique, arises from the pos- epigastric
terior layer of the thoracolumbar fascia, from the ante- Posterior artery and
rior two thirds or more of the intermediate line (lip) of layer of vein (cut)
the iliac crest and the lateral one half to two thirds of rectus sheath Site of deep
the folded-under edge of the external oblique aponeu- inguinal ring
rosis, together with the immediately adjacent and Arcuate line (origin of
closely related iliac fascia. The majority of the fibers Inferior internal
from the thoracolumbar fascia and the iliac crest course epigastric spermatic
superiorly and medially, which means that their direc- vessels fascia)
tion is perpendicular to the general direction of the
fibers of the external oblique. The most posterior fibers Superficial Cremasteric
insert on the inferior borders of the lower three (or circumflex and pubic
four) ribs and their costal cartilages. The rest of these iliac artery branches of
fibers end in an aponeurosis along a line which extends (cut) inferior
inferiorly and medially from the 10th costal cartilage Superficial epigastric
toward the crest of the pubis. In the upper two thirds epigastric artery
(to three fourths) of the abdomen, the aponeurosis artery (cut)
splits at the lateral margin of the rectus into a posterior Femoral sheath
layer, which passes posterior to the rectus abdominis Superficial (contains femoral
muscle, and an anterior layer, which passes anterior to external artery and vein)
it. These two layers join medial to each of the two pudendal Inguinal ligament
rectus abdominis muscles and blend with those of the artery (cut) (Poupart)
opposite side in the linea alba. In the lower one third of
the abdomen, the aponeurosis of the internal abdominal Inguinal falx Lacunar ligament
oblique does not split but passes entirely anterior to the (conjoint (Gimbernat)
rectus abdominis muscle to reach the linea alba. The tendon)
fibers arising from the margin of the external oblique
aponeurosis and the related iliac fascia are paler and Pectineal Pectineal
less compact and course downward and medially, ligament ligament
arching superior to the spermatic cord in the male (Cooper) (Cooper)
(round ligament in the female). This portion of the Lacunar Fat in retropubic
internal oblique is generally closely blended with the ligament space (of Retzius)
related portion of the transversus abdominis muscle and (Gimbernat)
tends to fuse with it to create a common, more or less
aponeurotic, insertion that passes anterior to the inser- Reflected Pectineal fascia
tion of the rectus muscle on the pubic crest and for a inguinal ligament Cremaster muscle and fascia Internal spermatic fascia
variable distance on the pecten pubis as the conjoint
Pubic tubercle Superficial fascia Cremaster muscle
External spermatic fascia (cut) of penis and and fascia (cut)
scrotum (cut) External spermatic fascia (cut)
Deep (Buck) fascia of penis

tendon (inguinal falx). The nerve supply of the internal The cremaster muscle is well developed only in the
abdominal oblique is by way of the lowest two or three male because it is an extension of the lower border of
intercostal nerves, as well as the subcostal, iliohypogas- the internal abdominal oblique muscle that travels into
tric, and ilioinguinal nerves. The actions of the internal the spermatic cord. Laterally it is thicker and fleshier
oblique are similar to those of the external oblique (see and attaches to about the middle of the turned-under
above), except that contraction of the muscle of one side edge of the external abdominal oblique aponeurosis and
would help to produce a rotation that would bring the to the inferior edge of the internal abdominal oblique
shoulder of the same side posteriorly if the pelvis were muscle. From here, the somewhat scattered muscle
fixed in place. fibers spread over the spermatic cord along with

12 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-12  Overview of Upper Digestive Tract

Anterolateral Abdominal POSTEROLATERAL ABDOMINAL WALL
Wall (Continued)
Serratus anterior muscle
connective tissue (cremasteric fascia) running between Infraspinous fascia
them to end at the pubic tubercle and the anterior layer
of the rectus sheath. The nerve supply of this muscle is Rhomboid major muscle
from the genital branch of the genitofemoral nerve and Auscultatory triangle
also a branch from the ilioinguinal nerve. The action of
the cremaster muscle is to lift the testis toward the Lateral cutaneous branch of
superficial inguinal ring. posterior ramus of T7 spinal nerve
Medial cutaneous branch of
The transversus abdominis is a broad thin muscle that posterior ramus of T7 spinal nerve
takes a nearly horizontal course around the inner side
of the anterolateral abdominal wall. It arises from (1) Trapezius muscle
the inner surfaces of the costal cartilages of the lower Latissimus dorsi muscle
six ribs by fleshy slips, which interdigitate with the slips External oblique muscle
that make up the costal origin of the diaphragm; (2) an
aponeurosis formed by the union at the lateral border Thoracolumbar fascia (posterior layer)
of the erector spinae muscle of the layer of the thora-
columbar fascia attached to the tips of the transverse Lateral cutaneous branch of
processes of the lumbar vertebrae and the layer of this subcostal nerve (anterior ramus of T12)
fascia attached to the tips of the spinous processes of
the same vertebrae (an indirect origin from the lumbar Lumbar triangle (of Petit)
vertebrae); (3) the anterior one half to three fourths of
the internal lip of the iliac crest; and (4) approximately Iliac crest
the lateral one third of the folded-under margin of the Lateral cutaneous branch
external oblique aponeurosis and the closely related of iliohypogastric nerve (L1)
portion of the iliac fascia. The muscular fibers termi- Superior clunial nerves (lateral
nate in a strong (for most of its extent) aponeurosis cutaneous branches of posterior
along a line that extends from deep to the rectus muscle rami of L1–L3 spinal nerves)
above and courses interiorly and slightly laterally to
emerge lateral to the rectus at about the level of the Gluteal aponeurosis over
umbilicus and then to extend variably toward the gluteus medius muscle
middle of the inguinal ligament. In the upper two thirds Gluteus maximus muscle
to three fourths of the abdomen, the aponeurosis passes
posterior to the rectus muscle, fusing with the posterior 9 Latissimus dorsi muscle
layer of the aponeurosis of the internal abdominal 10
oblique muscle, and ends by meeting the one of the Latissimus dorsi muscle (cut and turned back)
opposite side in the linea alba. Insertion occurs also on 11
the xiphoid process at the upper end of the linea alba. 12 Serratus posterior inferior muscle
In the lower one fourth to one third of the abdomen,
the aponeurosis passes anterior to the rectus muscle to Digitations of costal origin of
reach the linea alba. The lower fibers of the transversus latissimus dorsi muscle
abdominis muscle have a common insertion with the Digitations of costal origin of
lower fibers of the internal oblique, as described with external oblique muscle
the insertion of the latter muscle above. The transver- External oblique muscle (cut and turned back)
sus abdominis muscle is often described as having an Tendon of origin of transversus abdominis muscle
inferior free border that arches over the spermatic cord Internal oblique muscle
in the male (round ligament in the female) from the Lateral cutaneous branch of subcostal
origin on the external oblique aponeurosis to the pubic nerve (anterior ramus of T12)
attachment. The nerve supply of the transversus muscle Lateral cutaneous branch
comes from the anterior rami of the lower five or six of iliohypogastric nerve (L1)
intercostal and subcostal nerves as well as the iliohypo-
gastric, ilioinguinal, and genitofemoral nerves. The Iliac crest
actions of the transversus muscle are the same as those Superior clunial nerves (lateral
listed as being common to the external oblique and cutaneous branches of posterior
other large muscles of the abdomen. Unilateral con- rami of L1–L3 spinal nerves)
traction of one side of the transversus abdominis muscle Gluteus maximus muscle
will not produce appreciable rotation.
inferiorly. It has a superior and an inferior attachment, present between the umbilicus and the xiphoid process,
The rectus abdominis is a flat, vertical muscle, located each of which is called the origin of the muscle by some and, in about one third of the instances, one is found
just lateral to the anterior midline, which is wider and authors and the insertion by others. Several incomplete, below the level of the umbilicus. The superior attach-
thinner superiorly and becomes narrower and thicker zigzag, transversely running tendinous bands are present ment of the rectus muscle is to the anterior surfaces of
in the muscle, creating its distinctive appearance. These the fifth, sixth, and seventh costal cartilages, the xiphoid
are better developed on the anterior surface of the process, and the costoxiphoid ligament. These attach-
muscle and are closely attached to the anterior wall of ments fall more or less in a horizontal line. The inferior
the rectus sheath. The one at the level of the umbilicus (caudal) or pubic attachment of the rectus muscle is by
is segmentally related to the 10th rib. Two are usually a short tendon, a broader lateral portion of which ends

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 13

Plate 1-13  Upper Digestive Tract: PART I

ANTERIOR ABDOMINAL WALL: INTERNAL VIEW ANTEROLATERAL ABDOMINAL WALL

Anterolateral Abdominal Falciform ligament Peritoneum (cut edges)
Wall (Continued) Transversalis fascia and its cut edge Round ligament (ligamentum teres) of liver
and paraumbilical veins
on a roughened area on the pubic crest, extending from Diaphragm Umbilicus
the pubic tubercle to the pubic symphysis. The nar-
rower medial portion of the tendon is attached to the Arcuate line Left medial
front of the symphysis, where it interdigitates with the umbilical
one of the opposite side. The nerve supply of the rectus Rectus ligament
abdominis muscle comes from the anterior branches of abdominis (obliterated
the anterior rami of the lower six or seven intercostal muscle left umbilical
nerves that enter the deep surface of the muscle near artery)
its lateral edge to send cutaneous branches obliquely Inferior
through the muscle as muscular branches enter into epigastric Peritoneum
the formation of an intramuscular plexus. The branch vessels
from the 10th thoracic nerve usually enters the muscle Inguinal Transversalis
below the tendinous inscription at the level of the triangle fascia
umbilicus. The rectus abdominis muscle generally acts (Hesselbach) External and
in conjunction with the previously described muscles to Internal
compress the abdominal organs and during respiratory Transversalis oblique
expiration. However, it is particularly involved in pro- fascia (cut) muscles
ducing flexion of the vertebral column, bringing the Transversus
xiphoid and pubic bones closer together. Interfoveolar abdominis
ligament muscle
The pyramidalis is a small and seemingly unimportant Deep Right medial
muscle that is absent in 20% to 25% of the population. circumflex umbilical fold
It arises from the crest of the pubis, just anterior to the iliac vessels Median
line of attachment of the rectus muscle, and its fibers Deep umbilical
run superiorly and toward the linea alba, into which inguinal ring ligament
they insert as high as one third of the distance to the Cremasteric (obliterated
umbilicus. The pyramidalis is supplied by a branch and pubic urachus) and
from the subcostal nerve and, sometimes, also the ilio- branches of paraumbilical
hypogastric or ilioinguinal nerves. No biomechanical inferior veins in
importance is ascribed to this muscle, although it does epigastric artery median
tense the linea alba, anchoring it to the pubic bones. Testicular vessels umbilical fold
External iliac vessels
The rectus abdominis and pyramidalis muscles are Spermatic cord Umbilical
wrapped in a sheath formed, for the most part, by the Femoral sheath prevesical fascia
aponeuroses of the three large flat muscles of the Lacunar ligament (Gimbernat) Lateral umbilical fold
anterolateral abdominal wall, the make-up of which (contains inferior
differs in the lower one fourth to one third of the Pectineal ligament (Cooper) epigastric vessels)
abdomen from the make-up of the rest of its length. In Inguinal falx (conjoint tendon) Femoral nerve
the upper two thirds to three fourths of the abdomen, Iliopsoas muscle
the aponeurosis of the external abdominal oblique Umbilical artery External iliac vessels
muscle fuses with the anterior lamella of the aponeuro- (occluded part distal to this point) Supravesical fossa
sis of the internal abdominal oblique muscle to form
the anterior layer of the rectus sheath, and the aponeu- Transverse vesical fold
rosis of the transversus abdominis muscle fuses with the Obturator internus muscle
posterior lamella of the internal oblique aponeurosis to
form the posterior layer of the rectus sheath. The ante- Levator ani muscle
rior and posterior layers of the sheath fuse medial to
the rectus muscle in the linea alba, and, at the lateral Obturator nerve and vessels Bulbourethral (Cowper) gland
margin of the rectus muscle, the anterior and posterior Ureter (cut) embedded in deep transverse
layers come together at the line of the splitting of the perineal muscle
aponeurosis of the internal oblique. The posterior layer Anterior recess of ischioanal fossa
of the sheath does not extend superior to the costal Superior vesical artery Seminal vesicle
margin, so that the uppermost part of the rectus muscle Ductus (vas) deferens Prostate and external urethral sphincter muscle
lies directly on the chest wall. In the lower part of the Urinary bladder
abdomen, the aponeurosis of the internal oblique Perineal membrane
muscle does not split into two layers, and both it and
the greater part of the aponeurosis of the transversus the transversalis fascia is thought to fuse with the fascia The extraperitoneal fascia (subserous fascia) is thin
muscle pass anterior to the rectus muscle, so that only on the external surface of the transversus and to form and comparatively free from fat on the roof and antero-
the transversalis fascia forms the posterior layer of the rectus a sheet extending to the inguinal ligament. This fascia lateral abdominal wall, except in the lowest portion,
sheath in this area. Usually, the inferior margin of the extends deep to the inguinal ligament to form the ante- where it is loose and fatty to allow for the expansion of
definitely aponeurotic part of the posterior layer of the rior wall of the femoral sheath. Lateral to this, in the the bladder. In contrast to the situation on the roof and
sheath is an obvious margin, called the arcuate line. area where the transversus abdominis arises from the most of the anterolateral abdominal wall, the extraperi-
turned-under edge of the external oblique aponeurosis toneal tissue on the posterior wall of the abdominal
The transversalis fascia is thin and adherent in some and the related iliac fascia, the transversalis fascia fuses cavity is large and quite fatty, particularly around the
areas and thickened and more independent in others. with the iliac fascia. great vessels and kidneys.
At the arched lower border of the transversus muscle,

14 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-14  Overview of Upper Digestive Tract

INGUINAL REGION: DISSECTIONS

Inguinal Canal External oblique Lateral crus Medial crus Anterior view Linea alba
muscle and
The space occupied by the spermatic cord and its cover- aponeurosis Rectus sheath
ings as it passes obliquely through the anterolateral (anterior layer)
abdominal wall in the male is called the inguinal canal. Anterior superior Transversalis
A similar inguinal canal is present in the female; it iliac spine fascia within
transmits the round ligament of the uterus toward its Internal oblique inguinal
termination in the labia majora. For the sake of conve- muscle (cut and triangle (site of
nience, the description given here will be based on the reflected) direct inguinal
male. In general, it can be said that the canal and the Transversus hernia)
structures described in relation to it are much the same abdominis muscle Inguinal falx
in the female, although somewhat narrower. Deep inguinal ring (conjoint
(in transversalis tendon)
The inguinal canal is an oblique tunnel, 3 to 5 cm fascia)
long, through the muscular and deep fascial layers of Cremaster muscle Reflected
the anterior abdominal wall that lie parallel to and just (lateral origin) inguinal
above the inguinal ligament. The canal extends between Inferior epigastric ligament
the deep inguinal ring, located in the transversalis fascia vessels (deep to
approximately halfway between the anterior superior transversalis fascia) Intercrural
spine of the ilium and the pubic symphysis, and the super- Inguinal ligament fibers
ficial inguinal ring, located in the aponeurosis of the exter- (Poupart) External
nal abdominal oblique muscle just superior and lateral to Lacunar ligament spermatic
the pubic tubercle. The deep inguinal ring can be (Gimbernat) fascia on
described as a funnel-shaped opening in the transversa- Cremaster muscle spermatic cord
lis fascia, because it is the site at which this fascia is (medial origin) exiting
continued onto the spermatic cord to become the Superficial Superficial
innermost covering of the cord, the internal spermatic inguinal ring inguinal ring
fascia. The inferior epigastric vessels are just inferomedial Fundiform
to the deep inguinal ring, and the most lateral part of Pubic crest ligament of penis
the inferior border of the transversus muscle is just
superolateral to this ring. The superficial inguinal ring Posterior (internal) view Rectus sheath (posterior layer)
is formed by a splitting apart of the fibers of the external Arcuate line Medial umbilical ligament
abdominal oblique aponeurosis, with those fibers that
pass superomedial to the ring going to intermingle with Rectus abdominis muscle
similar ones of the opposite side and attach to the
anteroinferior surface of the symphysis pubis. This Anterior superior iliac spine
portion of the external oblique aponeurosis is called the Transversalis fascia
medial crus of the superficial ring. The fibers of the exter- (cut away)
nal oblique aponeurosis that pass inferolateral to the
superficial inguinal ring are the lateral crus of the ring, Iliopubic tract
which, in a sense, is the medial end of the inguinal
ligament. Inferior epigastric vessels
Inguinal (Hesselbach)
The lower border of the external abdominal oblique triangle (dashed line)
aponeurosis is folded under upon itself, with the edge Femoral nerve
of the fold (and variable added fibrous strands) forming Genital branch of genito-
the inguinal ligament. The fascia lata on the anterior femoral nerve and testicular
aspect of the thigh is closely blended to the full length vessels
of the inguinal ligament. Its lateral half, folded deep to Deep inguinal ring
the aponeurosis, is firmly fused with the iliac fascia as Iliacus muscle (fusing with psoas
the iliacus muscle passes into the thigh. As to the medial major muscle)
half of the inguinal ligament, the folded edge is actually External iliac vessels
formed by the fibers of the aponeurosis rolling under Femoral ring (dilated) (broken line)
in such a way that the fibers forming the inferolateral Psoas (major) muscle
margin of the superficial inguinal ring become the most Lacunar ligament (Gimbernat)
inferior fibers at the attachment to the pubic bone and Pectineal ligament (Cooper)
thus attach most interiorly on the pubic tubercle, Ductus (vas) deferens
whereas the fibers that were originally more inferior Accessory obturator vessels
attach higher up on the tubercle and in sequence along Obturator vessels
the medial part of the pecten pubis for a variable dis-
tance, with the lowest fibers in the aponeurosis attach- Pubic branches of inferior epigastric vessels
ing farthest laterally on the pecten. The portion of the Pubic symphysis
aponeurosis that runs posteriorly and superiorly from Hesselbach’s triangle by Carlos Machado after Frank Netter
the folded edge to the pecten pubis can be called the
pectineal part of the inguinal ligament, or the lacunar beyond these points of attachment. Those which con- aponeurosis. These fibers, called the intercrural fibers,
ligament. The fibers of the external oblique aponeuro- tinue from the pecten pubis superiorly and medially can be thought of as helping to prevent the split between
sis, described above, are attached to the pubic tubercle superficial to the conjoined tendon reach the midline and the two crura of the external oblique aponeurosis
and the pecten pubis and continue, to a varying extent, blend somewhat with the external oblique aponeurosis (the superficial inguinal ring) from extending farther
of the opposite side. They are called the reflected ingui- laterally.
nal ligament.
Another structure that is frequently described as
Lateral to the superficial inguinal ring, variable being formed by fibers from the external abdominal
fibrous strands course roughly perpendicular to the oblique aponeurosis, and which has considerable clini-
fibers of the external oblique aponeurosis and are cal significance as a firm structure to which sutures can
blended with the fibers of the superficial surface of this be anchored in the surgical repair of hernia, is the

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 15

Plate 1-15  Upper Digestive Tract: PART I

INGUINAL CANAL AND SPERMATIC CORD

Inguinal Canal (Continued) Testicular vessels covered by peritoneum External oblique muscle
Testicular vessels and genital branch of genitofemoral nerve Internal oblique muscle
pectineal ligament (Cooper ligament). This ligament runs Transversus abdominis muscle
along the sharp edge of the pecten pubis and has the Ductus (vas) deferens Transversalis fascia
effect of heightening this ridge. It is often described as Cremasteric vessels Extraperitoneal
being formed by fibers of the lateral part of the pectin- External iliac vessels covered by peritoneum fascia (loose
eal portion of the inguinal ligament (lacunar ligament) Ductus (vas) deferens covered by peritoneum connective tissue)
which, as they approach the pecten, turn sharply super- Inferior epigastric vessels Peritoneum
olaterally to run along it. The pectineal ligament can Medial umbilical ligament
also be interpreted as a building up of the periosteum (occluded part of umbilical artery) Anterior
along the pecten pubis, which is more in keeping with Umbilical prevesical fascia superior
what appears to be the situation in many cadavers. Urinary bladder iliac spine
Rectus abdominis muscle Origin of internal
The origins and insertions of the internal abdominal Pyramidalis muscle spermatic fascia
oblique muscle and the transversus abdominis muscle Median umbilical from transversalis
have been described previously, but certain details in ligament (urachus) fascia at deep
regard to the portions of these muscles related to the inguinal ring
inguinal canal merit additional description. The exact Superficial Ilioinguinal nerve
amount of the turned-under edge of the external inguinal ring
abdominal oblique aponeurosis (and the adjacent iliac
fascia to which this edge of the aponeurosis is closely Femoral Spermatic
related) from which these two muscles take origin is vessels cord
quite variable, and it may be difficult to separate muscles
in this area. The origin of the internal oblique muscle, Pubic symphysis (covered by Cremaster muscle
more times than not, extends far enough medially so intermingling fibers of external and cremasteric
that some fasciculi of the muscle are anterior to the oblique aponeurosis) fascia on
spermatic cord as its constituent structures come spermatic cord
together at the deep inguinal ring, thus reinforcing this Pubic tubercle Inguinal ligament (Poupart)
area to a certain extent. The origin of the transversus External spermatic fascia Intercrural fibers
abdominis muscle (if it can be adequately separated) enveloping spermatic cord
usually does not extend medially beyond the lateral Inguinal falx (conjoint tendon)
border of the superficial inguinal ring, if it extends even
that far. Because the conjoined tendon inserts on the posterior wall. The two openings, of course, are the ligament and related iliac fascia, form the anterior wall
pecten pubis and the crest of the pubis and thus along deep inguinal ring in the transversalis fascia at the inter- of the canal deep to the external oblique aponeurosis.
a line that angles from the pecten onto the crest, the nal end of the canal and the superficial inguinal ring in Superficial to the external oblique aponeurosis lie the
part of this tendon inserting on the pecten is in one the aponeurosis of the external abdominal oblique superficial fascia and the skin, which continue medially
plane and that inserting on the crest is in a somewhat muscle at the external end of the canal. The external beyond the anterior wall of the canal above the super-
different plane. The part of the conjoined tendon abdominal oblique aponeurosis, strengthened by the ficial inguinal ring. The floor (inferior boundary) of the
inserting on the pecten pubis is partially fitted to the intercrural fibers, is present in the entire length of the canal is formed in its medial two thirds to three quarters
contour of the spermatic cord, and it approaches the anterior wall of the canal. For approximately the lateral by the rolled-under portion of the external oblique apo-
pecten from posterior to the spermatic cord to meet one quarter to one third of the canal, fibers of the neurosis together with the lacunar ligament (pectineal
the lacunar ligament (pectineal part of the inguinal internal oblique muscle, which arise from the inguinal portion of the inguinal ligament), forming a shelf upon
ligament), which approaches the pecten from below the
spermatic cord.

The inguinal canal and the structures within it can
be further elucidated by thinking of this tubular tunnel
as having a roof, a floor, and anterior and posterior walls,
although, of course, because the tunnel is shaped to
accommodate a cylindrical structure (the spermatic
cord), no sharp boundary between any of the four walls
can be established. It should be further remembered
that the openings at the ends of the tunnel are not in
planes perpendicular to the long axis of the tunnel but
are in planes that form an acute angle with the long axis
of the tunnel, so that the posterior wall of the canal
extends farther medially than does the anterior wall and
the anterior wall extends farther laterally than does the

16 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-16  Overview of Upper Digestive Tract

Inguinal Canal (Continued) FEMORAL SHEATH AND INGUINAL CANAL
Transversalis fascia (cut edge)
which the spermatic cord rests. The transversalis fascia Extraperitoneal fascia
is present for the entire length of the posterior wall of the
canal. Toward the medial end of the canal, and thus Parietal peritoneum
reinforcing the part of this wall posterior to the super-
ficial inguinal ring, is the reflected inguinal ligament to Median umbilical
the extent present just anterior to the conjoined tendon ligament (urachus)
of the transversus and internal oblique muscles. A quite Medial umbilical ligament
variable expansion from the tendon of the rectus (occluded part of umbilical artery)
abdominis muscle (called by some authors the inguinal Inferior epigastric vessels
falx) fuses, to a variable extent, with the posterior aspect
of the conjoined tendon. All of the reinforcing struc- Deep circumflex iliac vessels
tures just described are, of course, anterior to the trans- Testicular vessels
versalis fascia. Posterior or deep to the transversalis Cremasteric artery
fascia are the loose extraperitoneal fascia and peritoneum, Ductus (vas) deferens
which continue across posterior to the deep inguinal
ring. At the lateral end of the canal, the inferior epigastric External iliac vessels
artery and vein are posterior to the canal in the extra-
peritoneal fascia as they are in relation to the medial Accessory obturator vessels (variable)
(inferomedial) margin of the deep inguinal ring. Overly- External oblique aponeurosis (cut)
ing these vessels, a thickening in the transversalis fascia
is variably present. A slight depression in the parietal Internal spermatic fascia on
peritoneum, as seen from within, is apt to be present at spermatic cord
the site of the deep inguinal ring. The roof of the inguinal Femoral nerve (deep to
canal can be said to be formed by the most inferior iliopsoas fascia)
fasciculi of the internal oblique muscle as they gradually Femoral vessels in femoral sheath
pass in a slightly arched fashion, from a position at their
origin anterior to the canal to a position at their inser- Falciform margin of saphenous
tion (by way of the conjoined tendon) posterior to the opening (cut and reflected)
canal. At the lateral end of the canal, the lower fasciculi
of the transversus abdominis arch similarly over the Urinary Ureter
canal. It should be pointed out that, although the bladder Genitofemoral nerve
description above of a roof and a floor of the canal can Pectineal
serve a useful purpose in talking about the canal, the ligament Transversalis
anterior and posterior walls of the canal, in a sense, (Cooper) fascia forms
come together superior and inferior to the canal, and anterior wall of
the roof and much of the floor are, perhaps, manufac- Lacunar femoral sheath
tured for descriptive purposes. ligament (posterior wall
(Gimbernat) formed by
The weakest area in the anterolateral wall in relation iliopsoas fascia)
to the inguinal canal is the superficial inguinal ring, Inguinal
which, to a varying extent, is reinforced by the reflected ligament
inguinal ligament, the conjoint tendon, and the expan- (Poupart)
sion laterally and inferiorly from the tendon of the
rectus abdominis muscle to the pecten pubis. This gen- Lateral femoral cutaneous nerve
erally weakened area, the inguinal (Hesselbach) trian- Iliac fascia
gle, through which a direct inguinal hernia will pass, is
a triangle bounded superolaterally by the inferior epi- Genital branch of genitofemoral nerve
gastric vessels, superomedially by the lateral margin of Femoral branch of genitofemoral nerve
the rectus, and inferiorly by the inguinal ligament.
Testicular vessels
Developmentally, the inguinal canal is established as External iliac vessels
an outpouching in the inferior part of the anterior Inferior epigastric vessels
abdominal wall, the processus vaginalis, containing all of Ductus (vas) deferens and cremasteric artery
the layers from the parietal peritoneum outward, in
preparation for the descent of the testes from their Pectineal ligament (Cooper)
origin along the posterior abdominal wall through the
Femoral ring
Transversalis fascia forms
anterior wall of femoral sheath

Lacunar ligament (Gimbernat)

Inguinal ligament (Poupart)

Lymph node (Cloquet) in femoral canal

Femoral sheath (cut open)

inguinal canal and into the scrotum. Originally, the it passes through the successive layers of the anterolat-
process was straight in an anterior-posterior direction, eral abdominal wall. The covering acquired from the
but further regional development causes it to become transversalis fascia is called the internal spermatic fascia.
oblique. The processus vaginalis normally loses its The spermatic cord is typically described as having
connection with the parietal peritoneum of the abdomi- passed inferior to the lower border of the transversus
nopelvic cavity, and all that remains of this is the abdominis. The covering derived from the internal
double-walled serous sac, the tunica vaginalis, that par- abdominal oblique muscle is the cremasteric muscle and
tially surrounds the testis. The outpouchings of the fascia. The covering of the spermatic cord and testis
other layers remain as coverings of the spermatic cord procured from the external abdominal oblique muscle
and testis which are picked up by the spermatic cord as is the external spermatic and intercrural fasciae.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 17

Plate 1-17  Upper Digestive Tract: PART I

Posterior Wall of L1 Caval opening
Abdominal Cavity L2 Diaphragm
L3 Central tendon of
The bodies of the five lumbar vertebrae, together with L4 diaphragm
the related intervertebral discs, form a distinct, longitu- L5
dinal, midline elevation in the posterior wall of the Esophagus and
abdominal cavity, which may actually come within a Anterior vagal trunks
relatively short distance (a few centimeters) of the inner inferior Right crus of
surface of the anterior abdominal wall. The interverte- iliac spine diaphragm
bral disks produce bulges in this elevation, and the
anterior longitudinal ligament, with the closely attached Rectococcygeus muscle Left crus of
crura of the diaphragm, covers its anterior surface. diaphragm
Just lateral to the lumbar vertebrae are the psoas major Pubic tubercle Median
and minor muscles (if present). Lateral to the psoas Rectum arcuate ligament
major muscle in the area inferior to the crest of the Urethra Vertebrocostal
ilium is the iliacus muscle, and in the area between the (lumbocostal)
12th rib and the crest of the ilium is the quadratus Perineal membrane trigone
lumborum muscle. Pubic symphysis Aorta and
thoracic duct
The psoas major muscle arises from (1) the anterior Lateral arcuate
surfaces of the bases and the inferior borders of the ligament
transverse processes of all of the lumbar vertebrae;
(2) the lateral aspect of the intervertebral disc above Medial arcuate
each of the lumbar vertebrae and from the adjacent ligament
parts of the vertebra above and the vertebra below each Sympathetic
of these discs; and (3) from tendinous arches stretching trunk
across the concavity at the side of the body of each of Quadratus
the first four lumbar vertebrae. This muscle courses lumborum
interiorly along the brim of the pelvis and passes infe- muscle
rior to the inguinal ligament to enter the thigh and Transversus
insert on the lesser trochanter of the femur. abdominis
muscle
Present in 40% to 60% of the cases, the psoas minor Internal oblique
muscle arises from the lateral aspect of the bodies of the muscle
12th thoracic and 1st lumbar vertebrae and the inter-
vertebral disc between them. It courses inferiorly on the External oblique
anterior aspect of the psoas major, ending in a long flat muscle
tendon that inserts into the pecten pubis and the ilio- Psoas minor
pectineal eminence. muscle
Psoas major muscle
The iliacus muscle fills much of the iliac fossa (which
actually forms the lateral wall of this part of the abdomi- Anterior superior
nopelvic cavity) and arises from the upper two thirds of iliac spine
this fossa, the inner lip of the crest of the ilium, the Iliacus muscle
anterior sacroiliac and iliolumbar ligaments, and the
base of the sacrum. Its fibers converge as they course Psoas minor tendon
inferiorly to insert, for the most part, into the lateral
side of the tendon of the psoas major muscle. Some of Inguinal ligament
the fibers also insert onto the femur just inferior and (Poupart)
anterior to the lesser trochanter. Because most of the Ischial spine
iliacus muscle inserts into the tendon of the psoas Obturator internus
major, the two muscles are often described as the muscle
iliopsoas muscle and, of course, have a common action. Tendinous arch of
levator ani muscle
The quadratus lumborum muscle arises from the pos- Opening for femoral vessels
terior part of the iliac crest (inner lip), the iliolumbar Lesser trochanter of femur
ligament, and the transverse process of the 5th lumbar Pectineal ligament (Cooper)
vertebra (and perhaps 4th, 3rd, and 2nd lumbar verte- Lacunar ligament (Gimbernat)
brae for a sometimes-demonstrable anterior layer of the
muscle), and inserts into the lower border of the medial Piriformis muscle
part (half or so) of the 12th rib, with some insertion
Coccygeus (ischiococcygeus) muscle
Levator ani muscle

into the transverse processes of the upper four lumbar Depending on where the posterior limit of the antero-
vertebrae. It draws the last rib inferiorly and thus acts lateral abdominal wall is arbitrarily located, the por-
as anchorage for the diaphragm to the crest of the ilium, tions of the transversus abdominis muscle (overlain by
and it also bends the lumbar portion of the lumbar spine the internal and external oblique muscles) just lateral to
laterally. Its anterior surface is covered by a variably the quadratus lumborum muscle can also be considered
thin, anterior layer of the thoracolumbar fascia. Its pos- as helping to form the posterior abdominal wall.
terior side is in contact with the thoracolumbar fascia’s
middle layer. The superficial structures of the lower part of the
back are, of course, external to what has been described
The posteroinferior part of the diaphragm may be here and would have to be traversed were the abdomi-
considered as part of the posterior abdominal wall. nal cavity approached from behind.

18 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-18  Overview of Upper Digestive Tract

Diaphragm Sternal part of diaphragm Anterior branch of left phrenic nerve
Anterior branch of right phrenic nerve Costal part of diaphragm
Central tendon of diaphragm
Right inferior phrenic artery Esophageal hiatus
Caval opening Fibers from right crus passing
to left of esophageal hiatus
Right crus of diaphragm Left inferior phrenic artery
Greater splanchnic nerve Recurrent branch to esophagus
Lesser splanchnic nerve Anterior branch
Lateral branch
Phrenic ganglion Left superior
suprarenal artery
Least splanchnic nerve Left phrenic nerve

Costal part Left crus of
of diaphragm diaphragm

The dome-shaped roof of the abdominopelvic cavity is Quadratus L1 Lumbocostal triangle
formed by a musculoaponeurotic septum, the dia- lumborum muscle L2
phragm, which also forms the floor of the thoracic L3 12th rib
cavity and thus is the partition between these two cavi- Psoas major muscle L4 Lateral arcuate ligament
ties. This unique muscular structure takes origin by its Sympathetic trunk
entire circumference from the inner aspect of the lower Celiac trunk Aortic hiatus Lumbar part of diaphragm
margin of the thoracic cage. The muscular fibers course Medial arcuate ligament
superiorly and inward to insert in the margins of the Transverse process of L1 vertebra
diaphragm’s central tendon. The sternal origin is, by way
of a fairly short, fleshy slip (a right and a left one), on Median arcuate ligament
the posterior aspect of the xiphoid process, which, on Abdominal aorta
its way to the anterior margin of the central tendon,
does not ascend nearly as much as do the fibers from The inferior vena cava passes through the caval opening The aortic hiatus (really a notch in the posterior margin
the other two areas of origin. In fact, depending on the at the junction of the right and middle leaflets of the of the diaphragm) is at the level of T12 and transmits
position of the individual and the degree of contraction central tendon in the most anterior and highest of the the thoracic duct and azygos vein in addition to the
of the diaphragm, the fibers from the sternal origin may three large openings, being at the level of the disc aorta. The greater and lesser splanchnic nerves pierce
even course inferiorly. between T8 and T9. It often transmits a branch of the the crura, and, in addition, the left crus is pierced by
phrenic nerve. The esophageal hiatus is in the muscular the hemiazygos vein.
The costal origin in general arises from the inner portion of the diaphragm just posterior to the central
surfaces of the costal cartilages and the adjacent parts tendon, a little to the left of the midline and about at Intervals at the origin where muscle is replaced by
of the lower six ribs by fibers from each that interdigi- the level of T10, and transmits the esophagus as well as areolar connective tissue occur at the sternocostal tri-
tate with the origin of the transversus abdominis the anterior and posterior vagal trunks to the abdomen. angle and, with great variation, at the lateral arcuate
muscle. The lumbar origin consists of a crus and a ligaments.
medial arcuate ligament and a lateral arcuate ligament on
each side. The crura begin as tendinous structures,
which attach to the anterior and lateral sides of the
upper lumbar vertebrae (one to three or four for the
right and one to two or three for the left) and related
intervertebral disks, blending with the anterior longitu-
dinal ligament. The right crus is stouter as well as longer
than the left and, as it becomes muscular, usually splits
to send a portion to the left of the esophageal hiatus. The
medial margins of the two crura converge to meet in
the midline to form an arch across the anterior aspect
of the aorta, the median arcuate ligament. The medial
arcuate ligament is a tendinous arch that appears as a
thickening in the fascia over the superior part of the
psoas major muscle, extending from the side of the body
of the second (or first) lumbar vertebra, where it blends
with the lateral margin of the corresponding crus to the
end of the transverse process of the first (or second)
lumbar vertebra. The lateral arcuate ligament is a thick-
ening in the fascia that covers the quadratus lumborum
muscle and reaches from the end of the transverse
process of the 1st (or 2nd) lumbar vertebra to the tip
and lower margin of the 12th (or 11th) rib.

The central tendon is a thin but strong and dense
aponeurosis, closer to the sternal origin than the costal
and lumbar origins. It is shaped somewhat like a thick
and widely opened V, with slight indentations, which
produce three leaflets. The fibrous pericardium is
blended with its superior surface.

Several openings (hiatuses) permit the passage of
structures between the thoracic and abdominal cavities.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 19

Plate 1-19  Upper Digestive Tract: PART I

PELVIC DIAPHRAGM: MALE

Superior view Inferior (arcuate) pubic ligament Hiatus for deep dorsal vein of penis
(viscera removed)
Pubic symphysis Transverse perineal ligament
Pubic crest (anterior thickening of

Perineal membrane)

Pubic tubercle Hiatus for urethra

Pecten pubis Muscle fibers from levator ani
to conjoined longitudinal muscle
Superior ramus of pubis of anal canal

Obturator canal Puborectalis Levator ani
Obturator fascia Pubococcygeus muscle
Iliopubic eminence Iliococcygeus

Floor of Abdominopelvic Acetabular Tendinous arch of
Cavity margin levator ani muscle

Anterior Obturator
inferior internus
iliac spine muscle

The outlet of the pelvis (inferior aperture of the pelvis) Wing (ala) Coccygeus
is, for the most part, closed by the slinglike structure of ilium (ischiococcygeus)
known as the pelvic diaphragm that, together with the Arcuate line muscle
urogenital diaphragm, gives the inferior and posteroin-
ferior support to the abdominopelvic viscera. As usually Ischial spine Piriformis muscle
described, the pelvic diaphragm consists of the right
and left levator ani muscles, the right and left coccygeus Sacroiliac joint Sacral canal Anterior sacral (pelvic) foramina
muscles, and the fascia on both surfaces of these Sacrum Anterior
muscles. sacrococcygeal
ligament
The levator ani muscle arises (1) from the pelvic Anorectal hiatus
surface of the pubis along a line from a little lateral
to the inferior part of the pubic symphysis toward ligaments, presents several openings, each of which is, the femur, where it inserts. Anterosuperior to the origin
the obturator foramen, (2) from the tendinous arch of the to a great extent, closed by muscle. The obturator inter- of the levator ani muscle, the obturator internus muscle
levator ani, which is a thickening of the fascia on the nus, a muscle of the lower extremity, covers the obtura- forms a portion of the wall of the pelvic cavity. The
pelvic surface of the obturator internus muscle along a line tor foramen except for the much smaller obturator piriformis, also a muscle of the lower extremity, arises
extending from the lateral end of the pubic origin of canal through which the obturator vessels and nerve from the pelvic surface of the sacrum between, and
the levator ani to the ischial spine, and (3) from the pelvic pass. It arises from the pelvic aspect of the obturator lateral to, the second, third, and fourth anterior sacral
surface of the ischial spine. In general, the fibers of the fascia and the adjacent bone and passes through the foramina and mostly fills the greater sciatic foramen in
right and left levator ani muscles run posteriorly, infe- lesser sciatic foramen (mostly filling this opening) on traversing this foramen on its way to insert on the
riorly, and medially, with varying degrees of obliquity, its way to the medial side of the greater trochanter of summit of the greater trochanter of the femur.
to come into relationship with each other in the midline
by inserting into the perineal body, as well as the ante-
rior and lateral sides of the coccyx, or to blend closely
with the midline viscera, interposed between the two
muscles. The levator ani can be described in at least
three parts: (1) The puborectalis muscle, has fibers insert-
ing into the perineal body, clasping the prostate in the
male and the vagina in the female. The remaining fibers
form a sling around the anorectal junction. (2) The
intermediate set of fibers, found lateral and slightly
superior to the puborectalis, form the pubococcygeus
muscle. It originates from the posterior aspect of the
pubic bone and the tendinous arch of the levator ani to
insert into the coccyx and anococcygeal ligament. (3)
The remainder of the levator ani muscle is the iliococ-
cygeus muscle, which originates from the tendinous arch
of the levator ani and inserts onto the lateral aspect of
the coccyx. The nerve supply of the levator ani muscle
is from the fourth sacral nerve by way of the perineal
branch of the pudendal nerve.

The coccygeus muscle, which is closely applied to the
deep surface of the sacrospinous ligament and is in
much the same plane as the iliococcygeus muscle, is a
flat triangular muscle arising from the ischial spine and
inserting into the margin of the lower two sacral seg-
ments and the first two segments of the coccyx. It
receives its nerve supply from the anterior primary
ramus of the fourth sacral nerve.

The bony framework of the true pelvis (pelvis minor),
supplemented by the sacrospinous and sacrotuberous

20 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-20  Overview of Upper Digestive Tract

Diaphragm ABDOMINAL WALL AND VISCERA: PARAMEDIAN (PARASAGITTAL) SECTION
(central tendon) Coronary ligament
Parietal enclosing bare area
peritoneum of liver

Liver T10 Esophagus
Lesser
omentum Superior recess of
omental
T11 bursa (lesser sac)

Peritoneum Hepatic portal T12 Omental (epiploic)
vein and hepatic foramen (of Winslow)
The peritoneum is the extensive serous membrane that, artery proper L1 Celiac trunk
in general, lines all borders of the abdominopelvic in right margin L2 Splenic vessels
cavity and reflects from the body wall onto the organs of lesser L3 Renal vessels
that are contained within it. A general concept that one omentum Pancreas
might have of the pleura or the serous pericardium can Omental bursa L4
be carried over to the peritoneum. In all of these situ- (lesser sac) Superior mesenteric
ations, the serous membrane lining the body wall is Stomach L5 artery
continuous with that on the surfaces of the viscera con- Middle S1 Inferior (horizontal, or
tained within the portions of the body cavity involved, colic artery S2 3rd) part of duodenum
and although one refers separately to parietal and vis- Parietal
ceral portions of the serous membrane, they are con- peritoneum Abdominal aorta
tinuous. Also, under normal circumstances, the organs (of anterior Parietal peritoneum (of
fill the respective portion of the body cavity so com- abdominal posterior abdominal wall)
pletely that the visceral and parietal portions of adjacent wall) Mesentery of
structures are separated from each other by only a thin Transverse small intestine
film of fluid. The peritoneal cavity of the female is the mesocolon
only place where an organ’s lumen is in direct contact Transverse Rectovesical
with the peritoneal space, as the opening of each uterine colon pouch
tube is open to the peritoneal cavity. Greater
omentum Rectum
The peritoneum is much more complicated in its Rectus
arrangement than either the visceral pleura or the abdominis Rectoprostatic
serous pericardium. This is essentially due to the fact muscle (Denonvilliers)
that parts of several viscera deform the peritoneal Small intestine fascia
serous membrane to various degrees in the course of Transversalis fascia Levator ani muscle
fetal development. The rotations of the gut, combined Fatty layer of
with the propensity of one free peritoneal surface to subcutaneous tissue Prostate
fuse with another free surface, result in complex changes (Camper fascia)
of the arrangement that lead to the mature appearance Membranous layer Deep External
of the abdominal organs. The stomach (to cite only one of subcutaneous Superficial anal
example of the manifold rearrangements in the viscero- tissue (Scarpa Subcutaneous sphincter
peritoneal relations) in its primary vertical position was fascia) muscle
attached by one double layer of peritoneum, the ventral Median umbilical
mesogastrium, to the ventral body wall, and by another ligament (urachus) Deep and superficial transverse
double layer, the dorsal mesogastrium, to the posterior perineal muscles
wall. When the stomach rotated, its original left side Pubic bone
became the anterosuperior surface and the original Deep (Buck) Bulbospongiosus muscle
right side the posteroinferior surface; the dorsal meso- fascia of penis Perineal membrane and bulbourethral (Cowper) gland
gastrium was swept toward the left to form an out- Urinary bladder
pouching of the peritoneal cavity, which presents itself Retropubic (prevesical) Puborectalis muscle (thickened medial
at an early developmental stage (6 weeks) as the omental space (cave of Retzius) edge of left levator ani muscle)
bursa (lesser sac), communicating with the rest of the
peritoneal cavity (greater sac) by only a small opening, Tunica vaginalis testis Testis
the omental foramen (of Winslow), located a little to
the right of the midline posteroinferior to the liver. informative approach for studying the peritoneal peritoneum continues onto the inferior surface of the
continuity and its relationship to the abdominopelvic diaphragm and along it until it is reflected to the liver
The best way to obtain a general concept of the viscera. as the superior (anterior) layer of the left triangular liga-
arrangement of the peritoneum is to trace it in three ment. From here it extends along the anterosuperior
planes, a midsagittal plane and two horizontal planes, In the midsagittal plane, the greater and lesser peri- surface of the liver, around the free margin of the liver,
one at the level of the pylorus and the other at the level toneal sacs must be pursued separately, because they are and onto its visceral surface, until it is reflected toward
of the umbilicus, in a preferably fresh specimen at not continuous anywhere in this plane. In following the the lesser curvature of the stomach as the anterior layer
the autopsy table. Lacking this opportunity, the use of cut edge of the greater sac, one can start with the parietal of the lesser omentum, which then advances onto the
these three planes still remains methodically the most peritoneum on the inner surface of the anterior wall at anterior surface of the stomach, leaving the latter as the
the level of the umbilicus. Progressing superiorly, the

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 21

Plate 1-21  Upper Digestive Tract: PART I

SCHEMATIC CROSS SECTION OF ABDOMEN AT MIDDLE T12

Superior epigastric vessels Linea alba Rectus abdominis muscle
Falciform ligament
Transversalis fascia 7th costal cartilage
Parietal peritoneum External oblique muscle
Diaphragm
Visceral peritoneum of liver

Liver
Costodiaphragmatic
recess of pleural
cavity

Proper hepatic artery Stomach
(bifurcation)
Lesser omentum
Gallbladder
Common hepatic duct Left gastric artery
and vein
Cystic duct Celiac ganglia
Intercostal vessels
and nerve Pleura

Hepatic portal vein Spleen

Omental foramen Gastrosplenic
(of Winslow) ligament with
Common hepatic artery short gastric
(retroperitoneal) vessels
Splenorenal ligament
Omental bursa with splenic vessels
(lesser sac)
Inferior vena cava Parietal peritoneum
Right crus of diaphragm on posterior wall
of omental bursa
Thoracic duct Intercostal muscles
Azygos vein
Left suprarenal gland
Hepatorenal recess
(Morison pouch) Abdominal aorta

Left kidney

Body of T12 vertebra

Right sympathetic trunk Iliocostalis Latissimus dorsi muscle
Anterior longitudinal ligament Longissimus Erector spinae
Spinalis muscle

Peritoneum (Continued) of the rectum to the posterior vaginal fornix, bounding where it leaves the stomach to extend for a variable
the rectouterine pouch (of Douglas). It passes up the distance into the greater omentum. This distance
anterior surface of the greater omentum. At the free posterosuperior aspect of the uterus, over the fundus of depends on the degree of fusion of the peritoneum
margin of the greater omentum, this layer turns supe- the uterus, and down on its anteroinferior aspect to which has taken place, typically not reaching beyond
riorly to become the posterior surface of the greater about the junction of the body and cervix, from whence the transverse colon. The peritoneum turns superiorly
omentum, which proceeds superiorly to the transverse it reflects onto the posterosuperior aspect of the bladder, on the anterior surface of the transverse colon, and
colon, where it appears to continue onto the posterior bounding the vesicouterine pouch. In both the male then, in the adult, it usually forms the anterior layer of
surface of the transverse colon and then as the pos- and the female, the peritoneum passes from the supe- the transverse mesocolon if the fusion of the primitive
terior layer of the transverse mesocolon. From the pos- rior surface of the bladder to the inner surface of the dorsal mesogastrium with the primitive mesentery of
terior layer of the transverse mesocolon, the peritoneum anterior body wall, a variable distance above the sym- the transverse colon has been complete. The transverse
turns interiorly from the lower border of the pancreas physis pubis, depending on the degree of distention of mesocolon comes to the posterior body wall just infe-
across the anterior surface of the third portion of the the bladder. From here it continues superiorly to the rior to the point at which the tracing of the lesser sac
duodenum and becomes the right (superior) layer of the point at which this tracing of the peritoneum was peritoneum was started.
intestinal mesentery. At its free margin the mesentery started.
entirely (except for the area of mesenteric attachment) In tracing the peritoneum in a horizontal section at
surrounds the small intestine and continues to the pos- In following the cut edge of the omental bursa’s peri- the level of the omental foramen, a start can be made
terior body wall as the left (inferior) layer of the mes- toneum in a midsagittal plane, a start can be made on with the greater sac peritoneum on the inner surface
entery. On reaching the body wall, it runs as the parietal the anterior surface of the pancreas, and the peritoneum of the anterior abdominal wall in the midline. Follow-
peritoneum of the posterior wall interiorly on the anterior can be traced superiorly from here onto the surface of ing the cut edge of the parietal peritoneum to the left
surface of the aorta and then on the vertebral column the diaphragm until it reflects from the diaphragm to along the inner surface of the anterolateral wall to the
to about the second sacral level, where it comes to lie the liver as the inferior (posterior) layer of the left tri- region of the posterior wall, it will pass onto the antero-
on the anterior surface of the rectum, from which, in angular ligament. From here it can be traced along the lateral surface of the left kidney, from where it reflects
the male, it is reflected onto the posterosuperior surface posterior and then inferior surfaces of the liver to the to the hilar area of the spleen, forming the external
of the bladder, bounding the rectovesical pouch. In the point at which it leaves the liver to go to the lesser layer of the splenorenal ligament, and then completely
female, the peritoneum passes from the anterior surface curvature of the stomach as the posterior layer of the surrounds the spleen except at the hilar area. From the
lesser omentum, which continues onto the posteroinfe- anterior margin of the hilum of the spleen, the perito-
rior surface of the stomach and to the greater curvature, neum passes to the stomach as the external layer of

22 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-22  Overview of Upper Digestive Tract

CROSS SECTION AT L3, 4

Rectus abdominis muscle

Branches of inferior epigastric vessels Linea alba

Rectus sheath

External oblique aponeurosis

Internal oblique aponeurosis Transversalis fascia
Parietal peritoneum
Transversus abdominis aponeurosis Greater omentum

Round ligament Transversus abdominis muscle
(ligamentum teres) of liver
Internal oblique muscle
Transverse colon
External oblique muscle
Small intestine (ileum) Omental appendices

Mesentery of Small intestine (jejunum)
small intestine Descending colon
Left paracolic gutter
Superior Testicular (ovarian)
mesenteric vessels vessels
Parietal peritoneum
Lymph node Left ureter
Left sympathetic trunk
Ascending colon Psoas minor muscle
Inferior vena cava Quadratus lumborum muscle
Right paracolic gutter Latissimus dorsi muscle
Psoas major muscle
Abdominal aorta Intermesenteric (aortic) plexus
Anterior Intervertebral disc between L3 and L4 vertebrae
longitudinal ligament Erector spinae muscle
Transversospinalis muscle
Right genitofemoral nerve

Tendon of origin of
transversus abdominis
muscle
Iliohypogastric
nerve
Ilio-inguinal nerve
Combined
Layers of
thoracolumbar Middle
fascia Posterior
Ligamentum flavum
Spinous process of L3 vertebra

Peritoneum (Continued) down just far enough to be encountered in the plane of follow from this point the parietal peritoneum to the
the tracing or whether the plane of tracing passes just left along the inner surface of the wall to the posterior
the gastrosplenic ligament. The peritoneum can then be inferior to the bare area of the liver. In the former case, wall, where it reflects onto the left side of the descending
followed along the anterosuperior surface of the the peritoneum would pass from the kidney as the infe- colon to cover also the anterior surface and right side of
stomach to the lesser curvature, where it leaves the rior layer of the coronary ligament to the liver, and this structure, from which it passes to the posterior
stomach as the anterior layer of the lesser omentum, would follow around the liver to its anterosuperior body wall. In early development the descending colon
which can be followed to the right until the free margin surface, where it would leave the liver as the left layer was suspended by the primitive dorsal mesentery, but
is reached a short distance to the right of the midline. of the falciform ligament, to go to the inner surface of peritoneal fusion during embryologic development
Here the peritoneum passes around the free margin of the anterior body wall and to the left to the point from brings it into the adult relationship to the peritoneum
the lesser omentum (anterior boundary of the omental which the tracing started. To complete the tracing in just described. The peritoneum continues to the right
foramen) to become the peritoneum of the omental this plane, one must follow the peritoneum from the on the posterior body wall to about the midline, where
bursa, which continues to the left, as the posterior layer right layer of the falciform ligament onto the anterosu- it reflects forward to form the left (inferior) layer of the
of the lesser omentum, to the lesser curvature of the perior surface of the liver, and to the right along this intestinal mesentery. The small intestine is completely
stomach, where it continues onto the posteroinferior surface to the superior layer of the coronary ligament, surrounded (except at its mesenteric attachment) in the
surface of the stomach, which it follows until it leaves along this to the diaphragm, and then anteriorly to the free margin of the mesentery; from here the perito-
the stomach to form the internal (lesser sac) layer of the right layer of the falciform ligament. If the plane of neum is traced posteriorly to the posterior body wall as
gastrosplenic ligament. From the spleen the perito- section passes just inferior to the bare area of the liver the right (superior) layer of the mesentery. Thereafter,
neum forms the internal layer of the splenorenal liga- as the peritoneum leaves the anterior surface of the the peritoneum can be followed to the right onto the
ment and then travels to the right anterior to the aorta inferior vena cava (the posterior boundary of the posterior body wall, until it reflects from here to cover
and the inferior vena cava. At the right margin of the omental foramen), it passes across the anterior surface the left, anterior, and right surfaces of the ascending
inferior vena cava, the peritoneum again becomes con- of the right kidney, then to the diaphragm, and forward colon. This structure was also suspended originally by
tinuous with the greater sac and continues to the right on the inner surface of the body wall to the falciform the primitive dorsal mesentery. From the right side of
onto the anterior aspect of the right kidney. From here ligament. the ascending colon, the peritoneum passes to the pos-
the tracing of the peritoneum could differ, depending terior body wall and then forward on the inner surface
on whether the bare area of the liver were to extend In tracing peritoneum in a horizontal section at about of the anterolateral abdominal wall until it reaches the
the level of the umbilicus, one can start at the midline midline, from where the tracing was started. Also in a
of the inner surface of the anterior abdominal wall and

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 23

Plate 1-23  Upper Digestive Tract: PART I

PERITONEUM OF POSTERIOR ABDOMINAL WALL

Inferior vena cava Hepatic Abdominal aorta and celiac trunk
(Common) bile duct and veins
hepatic artery proper Falciform ligament
Coronary ligament of liver
Right suprarenal gland Superior recess of omental bursa (lesser sac)
Attachment of transverse
mesocolon and right Attachment of lesser omentum and
gastro- left gastric artery
omental Left triangular
(gastro- Esophagus ligament of liver
epiploic)
vessels Gastro-
phrenic
Right ligament and
triangular left inferior
ligament phrenic
artery
Duo-
Peritoneum (Continued) denum Short gastric
Right vessels
section at about the level of the umbilicus, one would kidney
expect to find the greater omentum cut, which is Splenorenal
present as an island of peritoneum not connected in this Parietal (lienorenal)
section to the rest of the peritoneum. If the transverse peritoneum ligament
colon is hanging low enough, it too would be cut as an and splenic
island with its peritoneum continuous with that of the Root of vessels
greater omentum. mesentery Phrenico-
Common colic
Worthwhile additions to the general concept of the iliac artery ligament
distribution of the peritoneum, gained by tracing it in (retro- Pancreas and
several planes as done above, can be obtained by careful peritoneal) splenic artery
study of a view of the posterior half of the abdomino- Site of (retro-
pelvic cavity, in which all of the viscera (except the ascending peritoneal)
bladder and rectum) that invaginate the peritoneum to colon
any degree have been removed, cutting the peritoneum Attachment
along its lines of reflection from the posterior body wall External of transverse
or the anterior surfaces of the viscera and vessels that iliac artery mesocolon
do not project into the peritoneum. The right and left (retro- Site of
kidneys, the pancreas (except for the tip of its tail), the peritoneal) descending
second, third, and most of the fourth parts of the duodenum, colon
and the aorta and inferior vena cava do not project into Testicular
the peritoneal cavity to a significant degree. The peri- vessels Superior
toneum covers the inner surface of the abdominopelvic (retro- mesenteric
body walls as parietal peritoneum, except where it is peritoneal) vessels
lifted away from them by the structures just listed (the
bare area of the liver against the diaphragm, the ascend- Rectum Attachment
ing and descending colon, the roots of the mesentery, Urinary of sigmoid
the transverse mesocolon and sigmoid mesocolon, the bladder mesocolon
ureters and inferior mesenteric vessels, and the rectum and sigmoid
and bladder and, in the female, the uterus and broad vessels
ligaments, other folds in the pelvis, and folds on the Superior
inner surface of the anterior abdominal wall). The folds rectal vessels
on the inner surface of the anterior abdominal wall are Sacrogenital
the falciform ligament of the liver (a remnant of the fold
ventral mesentery, ventral to where the liver grew into (ligament)
it), running superiorly and a little to the right from the
umbilicus, with the ligamentum teres (obliterated Ureters (retroperitoneal) Lateral umbilical fold (contains
umbilical vein) of the liver in its free margin; the median Median umbilical fold (contains urachus) inferior epigastric vessels)
umbilical fold, projecting from the superior aspect of the Medial umbilical fold (contains
urinary bladder, running superiorly up the midline to occluded part of umbilical artery)
the umbilicus; the medial umbilical folds, also running to
the umbilicus and containing the obliterated right and supravesical fossa, whereas the one between each medial by peritoneum on its inner surface. This is because
left umbilical veins; and the right and left lateral umbili- and lateral umbilical fold is the epigastric fold. Lateral several viscera, major vessels, and a significant amount
cal folds, containing the inferior epigastric artery and vein of the lateral umbilical fold is the lateral inguinal fossa. of adipose tissue lie behind the peritoneum and most of
on each side (which may produce a slight elevation Parietal peritoneum is thus seen to be applied to prac­ the abdominal viscera project from the posterior wall
remindful of a fold by pulling the peritoneum a little tically the entire extent of the inner surface of the into the peritoneal cavity.
away from the body wall). The depression between anterolateral abdominal wall, and virtually any incision
the median and medial umbilical folds is called the through this wall will open into the peritoneal cavity. From the preceding description it is obvious that the
degree to which the various abdominal viscera are
Much of the diaphragm has parietal peritoneum on covered by peritoneum (visceral peritoneum) varies
its abdominal surface, but much less of the muscular along a spectrum in which peritoneum may cover just
portion of the posterior abdominal wall is directly lined part of one surface of the viscus in question to the other

24 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-24  Overview of Upper Digestive Tract

OMENTAL BURSA: STOMACH REFLECTED

Gastroomental (gastroepiploic) arterial Stomach (posterior surface)
anastomosis (enclosed in greater omentum) Caudate lobe of liver
Probe in superior recess of omental bursa
Inferior vena cava (retroperitoneal) Left gastric artery (in gastropancreatic fold)
Common hepatic artery Left inferior phrenic artery (retroperitoneal)
(in peritoneal fold) Gastrophrenic ligament
Left suprarenal gland (retroperitoneal)
Hepatoduodenal ligament
(right margin of lesser omentum) Gastrosplenic
(gastrolienal)
Probe in omental ligament
(epiploic) foramen
Spleen
Gallbladder
Diaphragm

Liver

Peritoneum (Continued)

extreme in which peritoneum covers the viscus entirely, Right colic Left colic
except for the area of attachment of a suspending (hepatic) flexure (splenic)
double-layered fold of peritoneum. “Retroperitoneal” Kidney (retroperitoneal) flexure
is a very commonly used descriptive term having the Phrenicocolic
general meaning of “behind the peritoneum,” which is Descending (2nd) ligament
well agreed upon, but some authors refer to certain part of duodenum Splenorenal (lienorenal)
organs as retroperitoneal that other authors would not Right gastroomental (gastroepiploic) ligament
designate in this fashion. Generally, “primarily retro- artery (covered by peritoneum) Tail of pancreas (intraperitoneal)
peritoneal structures” (e.g., ureter, kidney) are those Anterior superior pancreatico- Posterior layers of greater
that develop posterior to the peritoneal lining and never duodenal artery (retroperitoneal) Anterior layers (cut) omentum
develop a mesentery. “Secondarily retroperitoneal Transverse mesocolon
structures” once had a mesentery but lost it when the Head of pancreas (retroperitoneal) Body of pancreas (retroperitoneal)
organ was laid back along the body wall and the mes-
entery fused to a degree with the parietal peritoneum determining collections of fluid and the localization of contains the middle colic artery, branches of the right
(e.g., ascending colon, second portion of the duode- infection. and left colic arteries, accompanying veins, lymphatic
num). “Intraperitoneal structures” are those that are structures, autonomic nerve plexuses, as well as a con-
suspended from the posterior body wall by a mesentery The transverse mesocolon is the broad peritoneal fold siderable thickness of connective tissue.
containing blood vessels and nerves associated with the suspending the transverse colon from the posterior
organ (e.g., stomach, ileum). Additional details will be body wall. The root of the transverse mesocolon crosses the The sigmoid mesocolon is the mesentery of the sigmoid
given in the sections dealing with each organ or region. anterior surface of the right kidney, the second portion colon. When the peritoneum begins to surround the
of the duodenum, and the head of the pancreas, and large intestine near the crest of the ilium, the attach-
The mesentery is commonly taken to mean the mes- then passes along the lower border of the body and tail ment of the sigmoid mesocolon follows a fairly straight
entery of the small intestine (i.e., the jejunoileal portion of the pancreas superior to the duodenojejunal flexure, line from the posterior part of the left iliac fossa infe-
of the small intestine which is the portion having a to end on the anterior surface of the left kidney. It riorly and medially to reach the third sacral segment.
mesentery or a double-layered fold of peritoneum sus-
pending it from the posterior abdominal wall). The root
of the mesentery is about 15 cm in length, and its line of
attachment varies a bit with the shape of the duodenum,
but, in general, it courses from a little to the left of the
second lumbar vertebra inferiorly and to the right,
crossing the third part of the duodenum, the aorta, the
inferior vena cava, the right ureter, and the right psoas
major muscle to reach a point near the right sacroiliac
joint. The free or unattached border, which contains
the loops of the small intestine, is frilled out to such an
enormous degree that it may attain a length varying
from 3 m to more than 6 m. The distance from the
attached border to the free border measures 15 to
22 cm; it may definitely increase with age, probably
owing to stretching of the mesentery due to laxity of
the anterior abdominal wall. Between the two layers of
peritoneum on the two surfaces of the mesentery are
the superior mesenteric artery and its branches, the
accompanying veins, lymphatics, approximately 100 to
200 lymph nodes, autonomic nerve plexuses, connec-
tive tissue, and varying amounts of adipose tissue,
which is present in greater amounts near the root. The
mesentery divides the area below the transverse meso-
colon into two compartments, which are important in

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 25

Plate 1-25  Upper Digestive Tract: PART I

PELVIC CONTENTS: MALE

Superior view Linea terminalis of pelvis Linea alba Median umbilical fold and ligament (urachus)
Femoral ring Rectus abdominis muscle
Medial umbilical fold and ligament
Deep inguinal ring (occluded part of umbilical artery)

Pubic branch of inferior epigastric Inferior epigastric vessels and
artery (obturator anastomotic) lateral umbilical fold

Ductus deferens (in peritoneal fold) Urinary bladder and
transverse vesical fold
Transversalis fascia
Iliopubic tract
Testicular vessels (extraperitoneal)
(in peritoneal fold) Rectovesical pouch
Parietal peritoneum Ureteric fold
External iliac vessels Vesicosacral
(sacrogenital) fold
Seminal vesicle
(subperitoneal)

Rectum Cecal folds

Sigmoid colon Cecum
Left paracolic gutter Pararectal fossa
Sacral promontory
Descending colon Terminal ileum
Right paracolic
gutter

Root of mesentery
Ascending colon
Inferior vena cava

Abdominal External oblique
muscles
Internal oblique
Transversus abdominis Ureter
Quadratus lumborum muscle Testicular vessels
Psoas minor and major muscles Abdominal aorta
Superior hypogastric plexus
Sympathetic trunk Body of
L3 vertebra
Anterior longitudinal ligament

Peritoneum (Continued) monly on the left side. It also may be much shorter than peritoneum on the transverse colon, and the anterior
this, appearing as just a fringe on the greater curvature surface of the primitive transverse mesocolon, it
If, as is the case in the other extreme of the range of of the stomach, or it may be of some length and found appears, in the fully developed state, as though the “two
variation, the colon is closely bound down in the iliac folded in between coils of the small intestine, tucked layers” of peritoneum, running superiorly as the poste-
fossa, the line of attachment of the sigmoid mesocolon into the left hypochondriac area or turned superiorly rior layer of the greater omentum, separate from each
goes posteriorly along the pelvic brim until it crosses just anterior to the stomach. The superior end of the other to surround the transverse colon and continue as
the anterior side of the sacroiliac joint, and then left border is continuous with the gastrosplenic liga- the two layers of the transverse mesocolon. Frequently,
descends along the anterior aspect of the sacrum to the ment, and the superior end of the right border extends there is enough fusion in the four-layered primitive
level of its second to third segment. The sigmoid colon as far as the beginning of the duodenum. The greater greater omentum inferior to the transverse mesocolon
is enwrapped by the free margin of the sigmoid meso- omentum is usually thin, with a delicate layer of fibro- that no extension of the omental bursa is present
colon, which has its greatest width (distance from elastic tissue as its framework, and somewhat cribriform between layers. Close to the greater curvature of the
attached to free border) at its attachment to the first in appearance, although it usually contains some adipose stomach, the right and left gastroomental vessels course,
sacral segment. This width varies from about 5 to tissue and may accumulate a large amount of fat in anastomosing with each other in the greater omentum.
18 cm, although it occasionally may be as much as an obese individual. In the make-up of the greater The greater omentum, if of any length, has a great deal
25 cm between the layers of the sigmoid mesocolon omentum, the peritoneum of the omental bursa on the of mobility and can shift around to fill what would
through which run the sigmoidal and superior rectal posteroinferior surface of the stomach and the greater otherwise be temporary gaps between viscera or to
arteries, accompanying veins, lymphatics and auto- sac peritoneum on the anterosuperior surface of the build up a barrier against bacterial invasion of the
nomic nerve plexus, and connective tissue, which, of stomach meet at the greater curvature of the stomach peritoneal cavity by becoming adherent at a potential
course, includes varying amounts of adipose tissue. and course inferiorly to the free border of the greater danger spot.
omentum, where they turn superiorly to the transverse
The greater omentum is the largest peritoneal fold; it colon. Early in development, these two layers of elon- The lesser omentum, which can be subdivided into
may hang down like a large apron from the greater gated dorsal mesogastrium course superiorly in front of hepatogastric and hepatoduodenal ligaments, extends from
curvature of the stomach in front of the other viscera the transverse colon and transverse mesocolon to the the posteroinferior surface of the liver to the lesser
as far as the brim of the pelvis or even into the pelvis. anterior surface of the pancreas. Owing to fusions of curvature of the stomach and the beginning of the duo-
It may even extend into an inguinal hernia, most com- these two layers of peritoneum to each other and to the denum. It is extremely thin, particularly the part to the
left, which is sometimes fenestrated. The right side is

26 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-26  Overview of Upper Digestive Tract

PELVIC CONTENTS: FEMALE

Superior view Linea alba Median umbilical fold and ligament (urachus)
Rectus abdominis muscle
Ligament of ovary
Medial umbilical fold and ligament
Deep inguinal ring (occluded part of umbilical artery)

Femoral ring Inferior epigastric vessels and
Iliopubic tract lateral umbilical fold
(covered by peritoneum)
Round ligament of uterus Urinary bladder and
External iliac vessels transverse vesical fold

Broad ligament Uterus (fundus)
Uterine (fallopian) tube
Iliac fossa (false pelvis) Suspensory ligament
of ovary (contains
ovarian vessels)

Uterosacral fold
Ureteric fold

Ovary Cecal folds

Sigmoid colon Cecum
Left paracolic gutter Rectum

Abdominal External oblique Parietal peritoneum
muscles Internal oblique Transversalis
Transversus abdominis fascia
Right paracolic
Descending colon Abdominal aorta gutter
Superior hypogastric plexus Pararectal fossa
Quadratus lumborum muscle Body of L3 vertebra Terminal ileum
Psoas major and minor muscles Anterior longitudinal ligament Ascending colon
Root of mesentery
Inferior vena cava

Ureter
Ovarian vessels

Sympathetic trunk

Peritoneum (Continued) anterior layer of the transverse mesocolon, anterior sur­ it is the peritoneum on the caudate process of the liver,
face of the pancreas, left suprarenal gland, superior end and its inferior boundary is the peritoneum that covers
thicker and ends in a free, rounded margin, which con- of the left kidney, and, to the right of the esophageal the beginning of the duodenum and the hepatic artery.
tains the common bile duct to the right, the hepatic opening into the stomach, that part of the diaphragm
artery to the left, and the portal vein posterior to these supporting the caudate lobe of the liver. The horizontal Many extremely variable and inconstant fossae or
two, and forms the anterior border of the omental extent of the bursa stretches from the omental foramen recesses have been described which are of interest to
foramen. In addition to the structures just listed, the at the right to the hilum of the spleen at the left, the surgeon because of the possibility of herniation of
lesser omentum contains the right and left gastric arter- where it is limited by the splenorenal and gastrosplenic a loop of intestine into any one of them. The more
ies (close to the lesser curvature of the stomach) and the ligaments. Inferiorly, the bursa may extend about as common ones are located either in the region of the
accompanying veins, lymphatics, and autonomic nerve far as the transverse colon, its cavity having originally fourth portion of the duodenum or in the region of the
plexuses. The lesser omentum reaches the liver at the reached as far down as the free margin of the greater cecum and ileocecal junction. A relatively common
porta hepatis, and to the left of the porta hepatis it omentum before becoming obliterated by fusion of its “intersigmoid recess” is found on the left side of the
extends to the bottom of the fossa for the ligamentum layers. The portion of the bursa between the caudate line of attachment of the sigmoid mesocolon at the
venosum, the obliterated ductus venosus, which carried lobe of the liver and the diaphragm is called the angle that is present in this line when the colon is
oxygenated blood from the umbilical vein to the infe- superior recess, and the narrow portion from the tightly bound down in the iliac fossa.
rior vena cava. omental foramen across the head of the pancreas to
the gastropancreatic fold is called the vestibule of A characteristic of the peritoneum covering the sur-
The omental bursa (lesser sac of the peritoneum) is the bursa. faces of the various parts of the colon is the presence of
a large fossa, or outpouching, from the general perito- little outpouchings of peritoneum containing adipose
neal cavity. It is bounded in front, from superior to The omental foramen (of Winslow) is the opening by tissue, which are called omental appendages (appendices
inferior, by the caudate lobe of the liver, lesser omentum, which the omental bursa communicates with the epiploicae).
posteroinferior surface of the stomach, and anterior layer of general peritoneal cavity (greater sac). It is somewhat
the greater omentum (at least in part). Posteriorly, from circular and is usually large enough to admit one or two The parietal peritoneum is supplied by the nerves
inferior to superior, are the posterior layer of the fingers. Anterior to the foramen is the free margin of to the adjacent body wall and is thus pain sensitive.
greater omentum (the amount of this depends on the the lesser omentum, containing the common bile duct, The visceral peritoneum is insensitive to ordinary
variable inferior extent of the bursa), transverse colon, hepatic artery, and portal vein. Its posterior border is the pain stimuli but does respond to ischemia, distention,
peritoneum covering the inferior vena cava; superior to and inflammation. When moist surfaces of peritoneum
which are in contact become irritated, adhesions tend
to form that often become permanent.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 27

Plate 1-27  Upper Digestive Tract: PART I

ENDOPELVIC FASCIA AND POTENTIAL SPACES

Female: superior view (peritoneum and loose areolar tissue removed)

Median umbilical ligament (urachus)

Umbilical prevesical fascia Pubic symphysis

Pelvic Fascia and Medial umbilical ligament Inferior (arcuate) pubic ligament
Perineopelvic Spaces (occluded part of umbilical artery) Deep dorsal vein of clitoris
Rectus abdominis muscle
The steadily changing pressure and filling conditions in Urinary bladder and vesical fascia Retropubic (prevesical) space
the pelvis require adaptability of those structures that Superior vesical artery in Transverse perineal ligament (anterior
support the viscera within the funnel-like frame of the lateral ligament of bladder thickening of perineal membrane)
pelvis. Part of this support derives from the anorectal Linea terminalis of pelvis
musculature and the levator ani. But since these muscles Femoral ring Medial pubovesical ligament
are, to a great extent, involved in the sphincteric and Inferior epigastric artery Lateral pubovesical ligament
emptying functions of the anorectal canal, their sup- and Pubic branch Vesicocervical fascial fibers
porting tasks are assisted by the connective tissue struc- Superior fascia of pelvic
tures of the pelvic fascia, which have substantial tensile Deep inguinal ring diaphragm (superior
strength. The anatomic relationships of the pelvic fascia levator ani fascia)
and associated muscles are physiologically and surgi- Transversalis Obturator canal and
cally significant. The pelvic fasciae are divisible into a fascia obturator artery
visceral and a parietal portion. The former lies entirely Iliopubic
superior to the pelvic diaphragm, forming the fascial tract
investments of the pelvic viscera, the perivascular
sheaths, and the intervisceral and pelvovisceral liga- External
ments, which are described below. iliac
vessels
The parietal portion of the pelvic fascia may be
divided into parts that lie either superior or inferior to Deep
the levator ani muscle. Superior to the levator ani, pari- circumflex
etal pelvic fascia is a continuation of the parietal abdom- iliac
inal fascia. The iliopsoas fascia and the transversalis fascia vessels
of the abdomen are attached along the linea terminalis Tendinous
to the bony pelvis and then extend inferiorly into the arch of
pelvis over the inner surface of the obturator internus pelvic
muscle as the obturator fascia. Anteriorly, the transversalis fascia
fascia is attached to the inner surface of the pubic bones (reflected
and symphysis. The prevertebral fascia of the abdomen laterally)
continues inferiorly into the pelvis as the presacral fascia. Iliac
fascia
The superior layer of the pelvic diaphragm arises Ovarian
from the arcus tendineus of the levator ani muscle, which vessels in
is a thickening in the obturator fascia, running arc-wise suspensory
and convex inferiorly from the posterior surface of the ligament
pubic ramus (1 or 2 cm in front of the obturator of ovary
foramen) to a point just superior to the ischial spine.
From this arcus, the superior fascia of the pelvic diaphragm Iliacus muscle Obturator
spreads out to cover the superior (inner) surface of the Ureter internus
levator ani and coccygeus muscles. fascia
Psoas major muscle Tendinous arch of
Anteriorly, this fascia spans the infrapubic interval Internal iliac vessels levator ani muscle
in front of the transverse perineal ligament. The fascia Inferior vesical Tendinous arch of
descends just a few millimeters to form a small fossa, and vaginal arteries pelvic fascia
the bottom of which is pierced by the dorsal vein of the Uterosacral ligament
penis or clitoris, respectively. On each side of this small Hypogastric (neurovascular) sheath Cardinal (transverse cervical
fossa, a thickening in the fascia extends posteriorly from or Mackenrodt) ligament with
each side of the lower end of the symphysis pubis to the Middle rectal artery uterine artery
prostate in the male and to the bladder in the female. Cervix of uterus and uterine fascia
These thickened parts are the medial puboprostatic Vaginorectal fascial fibers
ligaments (or anterior true ligaments of the prostate) in Superior rectal artery (left branch) Presacral fascia (pulled away)
the male, to which correspond the medial pubovesical
ligaments (pubourethral or anterior true ligaments) of Rectum and rectal fascia
the bladder, in the female. The lateral puboprostatic or Rectovaginal (potential) space
pubovesical ligaments (or lateral true ligaments of pros-
tate or bladder) lie just posterior to this and consist of Presacral (potential) space (spread open) Vesicocervical and vesicovaginal
lateral reflections from the fascia to the prostate or Median sacral artery (potential) spaces
bladder, respectively.
pubovesical ligaments, continue backward in a slight around their free margins, fuses with the deep (supe-
The thickenings in the superior fascia of the pelvic curve, concave downward, gradually diverging to the rior) layer of the urogenital diaphragm. Here also it is
diaphragm, which make up the medial puboprostatic or region of the ischial spine. This constitutes on each side reflected upon the prostate and bladder in the male and
the arcus tendineus of the pelvic fascia, which lies consider- the vagina in the female as the visceral fascial sheaths
ably more medially and below the arcus tendineus of the of these respective organs.
levator ani. The superior fascia of the pelvic diaphragm
also continues medially and below its arcus tendineus. Posteriorly, the superior fascia of the pelvic dia-
Anterior to the rectum, it spans the interval between phragm surrounds the rectum as it passes through the
the crura of the pubococcygeus muscles and, coursing pelvic diaphragm. It is reflected there as a sheath upon
the rectum as the visceral (rectal) fascia, but it also blends

28 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-28  Overview of Upper Digestive Tract

Pelvic Fascia and Peritoneum SAGITTAL SECTION OF FASCIAL PLANES
Perineopelvic Spaces (Continued) Presacral space Denonvillier fascia (rectoprostatic fascia)
(retrorectal
space) Retrovesical space
Seminal vesicle
Presacral fascia Peritoneum
(parietal) Vesical fascia
Urachus)
Umbilical
prevesical
fascia
Transversalis
fascia

with the longitudinal rectal musculature and contrib- Rectal fascia
utes fibrous extensions to the formation of the fibro-
muscular, conjoined longitudinal muscle of the anal Prerectal
canal. The reflection takes place largely at the arcus space
tendineus of the pelvic fascia, but also more medially
and more inferiorly in the region where the viscera Rectal
begin to penetrate the pelvic diaphragm. fascia

Inferior to the levator ani, the obturator fascia con- Symphysis Rectus
tinues inferiorly on the medial walls of the pelvis below pubis sheath
the arcus tendineus of the levator ani muscle. It covers
the obturator internus muscle and is attached to the Scarpa
bony pelvis about the margins of that muscle. In its fascia
lower portion the fascia is split to form the more-or-less Camper
horizontal pudendal canal (Alcock canal), in which course fascia
the internal pudendal vessels and the pudendal nerve. Prevesical
Depending on when it leaves the pudendal nerve, the space
canal may also include the dorsal nerves of the penis. The (Retzius)
inferior fascia of the pelvic diaphragm is a comparatively
thin sheet that extends from the arcus tendineus of the Levator Submucous
levator ani muscle and covers the inferior surface of this ani muscle space
and the coccygeus muscle. It continues around the Superior levator Internal anal sphincter
lower rectum and the anal canal. It is reflected into the ani fascia
anterior recess of the ischioanal fossa. Inferior levator Conjoined
ani fascia longitudinal muscle
The perineal fascia consists of a superficial subcuta- Deep postanal space
neous and a deep membranous layer. The former is Superficial external Superficial Deep fascia of penis
continuous with the subcutaneous fat (Camper fascia) anal sphincter external anal sphincter and scrotum
of the abdominal wall; the latter is the superficial perineal Deep external anal sphincter Scrotal septum
fascia (Colles fascia), corresponding to the Scarpa fascia Subcutaneous fat in
of the abdomen. The superficial layer varies consider- ischioanal fossa Retroprostatic space
ably throughout the perineum. Over the anal triangle
it forms the fatty layer of the deep part of the ischioanal Intermuscular space Prostatic fascia (capsule) Transverse perineal ligament
fossa, whereas laterally over the ischial tuberosities, it is Subcutaneous
made up of fibrous fascicles that connect to the underly- external anal sphincter Superficial perineal fascia Dartos fascia of scrotum
ing bone and form, directly over the ischial tuberosities,
fibrous bursal sacs. The main part of the superficial Bulbospongiosus muscle External urethral sphincter muscle
perineal fascia has a firm attachment to the pubic rami
and to the posterior margin of the urogenital diaphragm. extends anteriorly to the superolateral border of the The uterosacral ligament extends inferiorly from the
It spreads medially across the urogenital triangle, con- bladder, where it splits into superior and inferior layers. hypogastric sheath. Laterally, it blends with the supe-
stituting the floor of the superficial perineal space, which These blend, respectively, with the superior and lateral rior fascia of the levator ani and medially with the
lies between it and the inferior layer of the uro- aspects of the vesical fascia. Anteriorly, the arch carries inferolateral aspects of the bladder or prostatic fascial
genital diaphragm and contains the superficial perineal the obliterated umbilical artery and superior vesical vessels capsule. In a sense, it thus constitutes a reflection from
musculature. to the urinary bladder as the lateral ligament of the the superior fascia of the levator ani to the vesical (vis-
bladder. Posteriorly, in the female, the hypogastric ceral) fascia along the tendinous arch of the levator ani, its
The visceral fascia invests, one by one, each of the sheath fuses with the suspensory ligament of the ovary anterior portion containing the lateral true ligaments of
pelvic organs, forming their fascial capsule (e.g., vesical containing the ovarian vessels. the bladder or prostate. Posteriorly, the transversely
fascia, prostatic fascia, vaginal-uterine fascia, rectal fascia).
It also contains the ligaments that connect these viscera
with each other and with the pelvic walls and floor, as
well as the perivascular sheaths. The latter consist of
the hypogastric sheath, which arises on each side from the
parietal pelvic fascia over a roughly triangular area in
the posterolateral angle of the pelvis and extends infe-
riorly to the spine of the ischium. This sheath contains
the internal iliac vessels (and a variable number of their
branches) and the ureter, as well as its accompanying
nerves and lymphatics. Anteriorly, the sheath is con-
tinuous with the tendinous arch of the pelvic fascia, which

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 29

Plate 1-29  Upper Digestive Tract: PART I

ISCHIOANAL FOSSAE Iliacus muscle and fascia

Iliopectineal line External iliac vessels Sigmoid colon

Pelvic Fascia and
Perineopelvic Spaces (Continued)

placed transverse cervical (cardinal) ligament of the uterus Obturator
extends from the uterosacral ligament, carrying the internus
ureter, inferior vesical vessels, uterine vessels, and auto- muscle and
nomic nerves. fascia

The presacral fascia extends medially from the hypo- Ureter Ischial tuberosity
gastric sheath sitting anterior to the sacrum and anterior Extraperitoneal Pudendal canal (Alcock)
sacrococcygeal ligament, lying in a more or less vertical (supralevator) contains internal pudendal
plane, in contrast to the superior and inferior wings, space (fibrofatty tissue) vessels, pudendal nerve,
which unfold in a nearly horizontal plane. Upon reach- and perineal nerve
ing the sides of the rectum, the presacral fascia splits
into two leaves that encircle the rectum as the rectal Fat body of Deeper part Tendinous arch of
(visceral) fascia. This fascia carries the superior and ischioanal Superficial levator ani muscle
middle rectal vessels, inferior hypogastric or pelvic nerve fossa (perianal) part Sacrogenital fold (uterosacral
plexus, and many lymphatics. in female)
Transverse fibrous Levator ani muscle and
The course of the pelvic muscles and the anorectal septum of ischioanal fossa superior and inferior fascia
musculature, together with the superior and inferior of pelvic diaphragm
fascia of the levator ani, give rise to a number of peri- Perianal space (external venous plexus)
neopelvic spaces, which require more than mere anatomic
recognition because they have a fundamental impor- Submucous space (internal venous plexus) Peritoneum (cut edge) forming
tance for an adequate concept of infectious and malig- floor of pararectal fossa
nant processes of the pelvis and perineum. As with the Intersphincteric groove (anocutaneous line) Rectal fascia
fasciae, these spaces are conveniently separated by Internal anal sphincter muscle
the levator ani muscle. Superior to the levator ani, in
the male, there are four main spaces: (1) the prevesical Conjoined longitudinal muscle External anal sphincter muscle
space (of Retzius), (2) the rectovesical space, (3) the bilat-
eral pararectal spaces, and (4) the retrorectal space. the urogenital diaphragm. The rectoprostatic (Denonvil- rior aspect of the hypogastric sheath marks the lateral
liers) fascia, originating from the undersurface of the boundary of the two anterior spaces and also the separa-
The prevesical space of Retzius is, in both sexes, a rectovesical peritoneal pouch and extending inferiorly tion from the lateral recess of the space of Retzius.
potentially large cavity surrounding the anterior and in a coronal plane, divides into two leaves, an anterior Inferiorly, the prerectal space terminates where the
lateral walls of the bladder. The main cavity in front of leaf, blending with the prostatic fascia or capsule, and rectal fascia attaches itself to the urogenital diaphragm
the bladder contains two superimposed anteromedian a posterior leaf, attaching below to the urogenital dia- or its thin superior fascia. The retroprostatic space
recesses and two lateral compartments. The upper phragm medially and to the hypogastric sheath laterally. (Proust space) terminates inferiorly in the same region
anteromedial recess lies posterior to the anterior Thus the retrovesical compartment can become subdi- but varies, depending on the very inferior limit of the
abdominal wall (i.e., behind the most medial parts of vided into the retrovesical space and retroprostatic space rectoprostatic fascia and its attachments to the prostatic
the transversalis fascia) and is roofed by the peritoneal anteriorly and the prerectal space posteriorly. The infe- capsule.
reflection from the dome of the bladder supported by
the urachus and the umbilical prevesical fascia. Its lateral
borders are demarcated by the obliterated umbilical arter-
ies. The lower recess, continuous with the one above,
lies posterior to the symphysis and pubic bones, ante-
rior to the bladder, with a floor formed by the pubo-
vesical ligaments in the female or the puboprostatic
ligaments in the male. The lateral recesses of the pre-
vesical space are bounded by a lateral wall formed by
the obturator fascia and the superior fascia of the
levator ani, and a median wall presented by the bladder
and the lateral ligaments of the bladder. They contain
the ureter and the main neurovascular supply to the
bladder and, in the male, the prostate. The floor of the
lateral recess is the superior fascia of the levator ani.
Posteriorly, the lateral recess of the prevesical space
extends to the hypogastric sheath in the region of the
ischial spine. The roof is formed by the tendinous arch
of pelvic fascia covered by the peritoneum, where these
tissues are reflected from the lateral pelvic wall.

The retrovesical compartment in the male, divisible
into three subspaces, lies between the bladder and the
prostate, covered by the vesical and prostatic fasciae
anteriorly, and the rectal fascia covering the rectum
posteriorly. Its roof is formed by the rectovesical recess or
pouch of the peritoneum, which comes into existence
by the continuity of the peritoneal reflection from the
rectum to the bladder. Its floor is the posterior part of

30 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-30  Overview of Upper Digestive Tract

Pelvic Fascia and ACTUAL AND POTENTIAL PERINEOPELVIC SPACES Presacral Rectal
Perineopelvic Spaces (Continued) fascia fascia
Sagittal section Visceral Presacral space
peritoneum

Vesical fascia
Rectal
fascia

In the female, as in the male, the area between the Retropubic
bladder and the rectum is divided into three spaces. The (prevesical)
dominant dividing structure, however, is not the recto- space (of Retzius)
prostatic fascia but the much more substantial vagina,
cervix, and uterus. Anterior to these structures, two Recto- Retrovesical
spaces come into existence, the vesicocervical space supe- vesical Prerectal
riorly and the vesicovaginal space inferiorly. They are space Retroprostatic
separated by a fascial septum, the supravaginal septum
or vesicocervical ligament, which forms the floor of the Sphincter urethrae
vesicocervical space and the roof of the vesicovaginal
space. The vesicocervical space is roofed by the utero- Deep and superficial Rectovesical
vesical fold of the peritoneum and extends inferiorly to transverse perineal muscles or rectoprostatic
the point where the urethra and vagina are in apposition
superior to the urogenital diaphragm. In the floor of External Deep (Denonvilliers)
this space, the medial and lateral pubovesical ligaments anal Superficial fascia (septum)
surround the urethra. Laterally, the vesicovaginal space sphincter Subcutaneous
is limited by the strong fascial connections between the muscle*
bladder and the cervix.
Deep (Buck) fascia of penis Levator ani
In the female, the rectovaginal space is farther from the muscle and
anterior compartments because the substantial mass of Superficial perineal (Colles) fascia Superficial fascia of pelvic
the cervix, uterus, and vagina provide more separation Superficial perineal compartment (space or pouch) postanal space diaphragm
than in the male. Whether or not the small area between (part of perianal Deep postanal
the rectum and the genital organs can be divided into *Parts variable and space) space
a retrovaginal and a prerectal space is a controversial often indistinct Anococcygeal
question of no practical significance. Of more practical Submucous space body (ligament)
importance is the fact that the rectovaginal space is Perianal space
roofed by a deep peritoneal fold that forms the recto-
uterine pouch (of Douglas). The boundaries of this space Bulbospongiosus muscle and deep
are, anteriorly, the vaginal fascia and, posteriorly, the perineal (Gallaudet) fascia
rectal fascia. Laterally, the space extends to the fusion of
the vaginal and rectal fascial collars, which, in this Perineal membrane,
region, form the wings of the vagina. The space termi- Deep transverse perineal muscle, and
nates inferiorly at the line of fusion between the poste- Superficial transverse perineal muscle
rior vaginal wall and the anal canal. In this region (cut away) to expose
numerous fascial and muscular elements fuse, terminat- Anterior recess of ischioanal fossa
ing inferiorly at the perineal body, also called the “central Preanal communication (inconstant)
point of the perineum.” between right and left ischioanal fossae

The pararectal space extends on each side from the Pus in ischioanal fossa
rectoprostatic fascia (male) or the cardinal ligament
(female) to the presacral fascia. It lies on the supraanal Posterior communication between right
fascia covering the superior surface of the pubococ- and left ischioanal fossae via deep
cygeus muscle, alongside the inferolateral parts of the postanal space deep to anococcygeal
rectum or its fascial enclosure. Its roof is made up, in body (ligament)
both sexes, of the peritoneum reflected from the lateral Gluteus maximus muscle and
aspects of the rectum to the pelvic walls, forming the Sacrotuberous ligament
floor of the pararectal peritoneal fossa. (cut)
Posterior recess of ischioanal fossa
The presacral space, similar in both sexes, constitutes
the interval between the parietal pelvic fascia, covering Perineal view
the sacrum as well as the piriformis, coccygeus, and
pubococcygeus muscles, and the presacral fascia, which Spread of perineal abscess in perineal spaces
envelops the rectum as the rectal fascia. Where the pos-
terior rectal wall lies almost horizontally, the ventral and extending from the anorectal muscle ring to the circumference of the anal canal, from the junction of
lining of the presacral space is produced by the rectal dentate line, is the highest or most cranial. Its practical the external sphincter with the levator ani to the intra-
fascial collar. Superiorly, the space becomes continuous significance is explained by its contents: the terminal muscular groove. Abscesses in this intermuscular space
with the prevertebral-retroperitoneal areolar tissue. A anastomotic network of the internal rectal venous may develop as a result of infection of the perianal
strong lateral barrier for this space is provided by the plexus and a rich lymphatic plexus, both embedded in glands expanding within it. Both the submucous and
attachment of the hypogastric sheath to the parietal a supportive fibroelastic connective tissue. intermuscular spaces are not interfascial but, rather,
fascia, a fact that explains why retrorectal abscesses are intravisceral.
more apt to rupture into the rectum than to penetrate A potential but not truly anatomic space, with some-
into the space superior to the levator ani. what ill-defined borders, lies within the conjoined lon- The perianal space is located between the skin and
gitudinal muscle between the internal and external anal the transverse septum of the ischioanal fossa. Its bound-
In the spaces inferior to the levator ani, the submucous sphincters. This intermuscular space surrounds the entire aries, projected to the surface, correspond to the anal
space, encircling the sphincteric portion of the rectum

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 31

Plate 1-31  Upper Digestive Tract: PART I

Hip

Pelvic Fascia and
Perineopelvic Spaces (Continued)

Mesorectal fascia

triangle. Anteriorly, the space extends to the posterior Rectal cancer
border of the superficial transverse perineal muscle and Mesorectum
laterally as far as the ischial tuberosities. Medially, the
perianal space is confined by the anoderm superiorly as Sacrum
far as the latter’s firm attachment to the internal anal Axial MRI showing rectal cancer, surrounding mesorectum, and mesorectal fascia
sphincter. Numerous fibrous extensions from the con-
joined longitudinal muscle, which pass through the USL
subcutaneous external anal sphincter, transverse the
perianal space. It is important to note that, circuma- Douglas
nally, the perianal space reaches to the inferior end of pouch
the internal sphincter, within the subcutaneous external
anal sphincter. The space contains the external rectal Endometriotic PPF
venous plexus and superficial perianal lymphatics. Pos- R lesion Ur
teriorly, extending as far as the coccyx, the perianal
space changes its name and becomes the superficial post- PPF
anal space, which extends from the anal canal to the
subcutaneous tissue inferior to the extensions of the Pararectal
superficial external anal sphincter, known as the anococ- space
cygeal ligament, as it attaches to the posterior surface of Surgical view of right extraserosal pelvic fascia resection. PPF = parietal pelvic fascia; R = right; Ur = ureter;
the coccyx. It is noteworthy that the perianal space of USL = uterosacral ligament. (From Ballester M, Belghiti J. Surgical and clinical impact of extraserosal pelvic
each side communicates with its counterpart of the fascia removal in segmental colorectal resection for endometriosis. J Minim Invasive Gynecol 2014;
opposite side via this superficial postanal space inferior 21:1041-1048.)
to the anococcygeal ligament in just the same fashion
as the ischioanal fossae of each side communicate This deep postanal space is also known as the posterior space is filled with adipose tissue in a matrix of thin
superior to this ligament via the deep postanal space. communicating space, because through it communicate collagenous fibrils. The inferior rectal vessels and
Posteriorly, the relationships to the extensions of the the right and left ischioanal fossae. The deep postanal nerves cross each space obliquely from its posterolateral
conjoined longitudinal muscle and the fibers of the cor- space is thus the usual pathway for purulent infections angle en route from the pudendal vessels and nerves in
rugator cutis ani confine abscesses and fistulas compli- to spread from one ischioanal fossa to the other, result- the obturator canal to the anal canal.
cating anal fissures to the superficial tissues. ing in the semicircular or “horseshoe” posterior anal
fistula. The floor of the ischioanal space posterior to The superficial and deep compartments of the uro-
The largest and most important of the spaces inferior the urogenital diaphragm is the transverse septum of genital diaphragm occupy the space within the pubic
to the levator ani muscle are the paired ischioanal fossae the ischioanal fossa. In the anterior recess the floor is arch and contain the urogenital musculature that is in
(average 6 to 8 cm anteroposteriorly, 2 to 4 cm wide, 6 formed by the urogenital diaphragm. The ischioanal close functional relationship to the pelvic diaphragm
to 8 cm deep). Each of these is irregularly wedge- and the anorectal sphincters.
shaped, with the apex at the pubic angle and the base
at the gluteus maximus muscle. The superomedial wall
is formed by the circumanal and infraanal fasciae cover-
ing the superficial and deep portions of the external anal
sphincter and the superimposed puborectalis and pubococ-
cygeus portions of the levator ani muscle. The attach-
ments of this muscle and the infraanal fascia to the
urogenital diaphragm mark the medial wall of the ante-
rior extension (Waldeyer space), which extends anteri-
orly into the space above the urogenital diaphragm. At
the most cranial point of the ischioanal fossa, the inner
wall joins the outer wall, which is formed by the obtura-
tor fascia, overlying the obturator internus muscle, and
farther inferiorly by the ischial tuberosity. The infraanal
fascia covering the iliococcygeus muscle is the roof
of the ischioanal fossa. The coccyx, sacrospinous liga-
ment, sacrotuberous ligament, and overlapping gluteus
maximus muscle constitute the base or posterior wall of
the fossa. These structures thus confine the posterior
extension of the ischioanal fossa, which has, posteriorly
to the anal canal, no medial walls. The fossae of each
side communicate with each other by what is known as
the deep postanal space, which lies superior to the anococ-
cygeal ligament or posterior extension of the external
anal sphincter and inferior to the levator ani muscle.

32 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-32  Overview of Upper Digestive Tract

ARTERIES OF POSTERIOR ABDOMINAL WALL
Inferior phrenic arteries Recurrent branch to esophagus
Celiac trunk with common hepatic,
left gastric, and splenic arteries Superior suprarenal arteries
Middle suprarenal artery
Middle suprarenal artery
Superior suprarenal arteries Superior mesenteric artery
Inferior
Inferior suprarenal
suprarenal artery artery

Right Left renal
renal artery artery

Blood Supply of Psoas major Testicular
the Abdomen muscle (cut) (ovarian)
arteries
The aorta enters the abdomen by passing posterior to Quadratus
the median arcuate ligament of the diaphragm at the lumborum
level of T12. Its first branches are the paired inferior muscle Abdominal
phrenic arteries, which commonly originate between the aorta
diaphragmatic crura and course to the inferior aspect of
the dome of the diaphragm, where they divide into Subcostal Inferior
anterior and posterior branches. The latter of these artery mesenteric
anastomose with the intercostal arteries, whereas the
former anastomose with twigs of the inferior phrenic 1st to 4th artery
artery, as well as the musculophrenic, pericardiacophrenic, right lumbar
and internal thoracic arteries. Communications also exist, arteries Left colic
through the coronary ligament and bare area of the Common artery
liver, with the hepatic arterial system. The size and iliac arteries Sigmoid
origin of the inferior phrenic arteries vary greatly. arteries
Their caliber ranges from 1 to 4 mm. They may exit Iliolumbar
bilaterally (60%) from either the aorta or celiac artery, artery Superior
or one from the former and the other from the latter. rectal
They may emerge as a common trunk (40%), either Lateral artery
from the aorta (20%), from the celiac artery (18%), or sacral
from the left gastric artery (2%), before branching into arteries Median
left and right inferior phrenic arteries. sacral
artery
From the trunk of the posterior branch of the inferior External Internal
phrenic artery, multiple superior suprarenal arteries arise, iliac artery iliac
which, with the middle suprarenal artery (from the aorta) Testicular artery
and inferior suprarenal artery (from the renal or acces- (ovarian) artery Superior
sory renal arteries), will supply blood to the suprarenal Ascending gluteal
(adrenal) gland. Another important vessel is the recur- branch of artery
rent esophageal branch, which is given off by the left deep
inferior phrenic artery shortly after it has passed poste- circumflex Umbilical
rior to the esophagus. The right inferior phrenic artery iliac artery (patent
gives off several branches that supply oxygenated blood Superficial part) artery
to the inferior vena cava. circumflex giving rise
iliac artery to superior
From the posterior surface of the aorta, opposite the vesical
four upper lumbar vertebral bodies, arise four lumbar arteries
arteries, either via a common trunk or separately on Inferior
each side. Because the aorta ends at the L4 level, a fifth epigastric
pair of lumbar arteries frequently originate from the artery Obturator
middle sacral or internal iliac arteries. The lumbar artery
arteries curve around the vertebral bodies and pass pos-
terior to the sympathetic trunk, psoas major, and qua- Pubic, Transversalis Inferior vesical
dratus lumborum muscles, except for the fourth lumbar Cremasteric fascia (cut) artery and
segmental artery, which often traverses anterior to the branches of inferior artery to
latter. The right lumbar arteries travel posterior to the epigastric artery ductus
inferior vena cava, and L1 and L2 arteries run posterior Superficial epigastric artery (cut) deferens
to the cisterna chyli. Each lumbar artery gives off a long Inferior
posterior branch, which, via medial, lateral, and spinal Femoral artery epigastric artery
rami, supplies the skin and muscles of the back, the
spinal ligaments, and the spinal cord. Leaving the Ductus deferens and testicular artery (cut) Anterior Middle rectal artery
lateral border of the quadratus lumborum muscle, Superficial external pudendal artery abdominal wall Internal pudendal artery
the lumbar arteries continue between the transversus Deep external pudendal artery (turned down) Inferior gluteal artery
abdominis and internal abdominal oblique muscle
layers. As they travel toward the rectus abdominis Medial umbilical ligament
muscle, they release lateral cutaneous and anterior cuta- (occluded part of umbilical
neous branches and anastomose with the lower intercos- artery)
tal, iliolumbar, and superior and inferior epigastric arteries
and the ascending branch of the deep circumflex iliac artery. The lumbar arteries participate in an arterial circle kidneys, suprarenal glands, and proximal ureters. The
formed by adipose capsular branches from the renal, gonadal (testicular or ovarian) vessels exit the anterior
suprarenal, and gonadal arteries. surface of the aorta inferior to the renal arteries at a
level varying from L1 to L3, but they may occasionally
The unpaired, visceral branches from the abdominal arise from a suprarenal, phrenic, superior mesenteric,
aorta that feed the foregut, midgut, and hindgut are the lumbar, common iliac, or internal iliac artery. They may
celiac, superior mesenteric, and inferior mesenteric appear as a duplicated artery (17%) on one side or, less
arteries, respectively. The renal arteries exit the aorta frequently, on both sides. An important abnormality
at the level of L1 or between L1 and L2 and supply the

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 33

Plate 1-33  Upper Digestive Tract: PART I

ARTERIES OF ANTERIOR ABDOMINAL WALL Subclavian artery
Axillary artery Internal thoracic arteries

Lateral thoracic artery

Blood Supply of the
Abdomen (Continued)

concerns an arched gonadal artery (arched testicular Anterior Pericardiaco-
artery of Luschka), which originates from the aorta intercostal phrenic artery
posterior and inferior to the renal vein but ascends to arteries with phrenic
curve superiorly and descends anterior to the renal vein. nerve
External
The aorta divides at the level of the lower third of Internal Branch to
the L4 vertebra into the approximately 6 mm–wide Innermost falciform
common iliac arteries, the lengths of which vary from 1 Intercostal ligament of
to 9 cm. Up to the point at which they divide into muscles liver
external and internal iliac arteries, the common iliac Anastomoses with Musculo-
arteries have no branches, except for small, unnamed lower intercostal, phrenic
branches to the peritoneum and subperitoneal tissue. subcostal, and lumbar arteries
arteries Diaphragm
The superior epigastric and musculophrenic arteries Superior
(both terminal branches of the internal thoracic artery) External, epigastric
supply the anterolateral wall superiorly. The latter Internal arteries
vessels travel inferiorly in a space posterior to the lower oblique Transversus
costal cartilages and send branches to the seventh to muscles abdominis
ninth intercostal spaces, the lower pericardium, and the Transversus muscle and
superior region of the abdominal muscles. Terminating abdominis muscle aponeurosis
at the 10th and 11th intercostal spaces, they anastomose Ascending branch Rectus
with the intercostal and subcostal arteries, with additional of deep circumflex abdominis
small connections to the lumbar and deep circumflex iliac iliac artery muscles
arteries. A branch piercing the diaphragm communi- Superficial Internal
cates with the anterior ramus of the inferior phrenic circumflex iliac artery oblique muscle
artery. The superior epigastric artery, entering the Superficial External
rectus sheath posterior to the seventh costal cartilage epigastric artery (cut) oblique muscle
and descending posterior to the rectus abdominis Femoral artery Posterior layer
muscle, ramifies to supply this muscle and gives off a of rectus sheath
number of small cutaneous branches. It anastomoses Cremasteric and testicular Arcuate line
with the inferior epigastric artery. arteries and artery to ductus Inferior
deferens in spermatic cord epigastric
The main vessels that feed the inferior abdominal artery
wall are the inferior epigastric and deep circumflex iliac leaving the main artery near the anterior superior iliac
arteries. Both arise from the external iliac artery, the spine, anastomoses with the subcostal, lumbar, and Superficial
former on its medial side and the latter on its lateral lower intercostal arteries; other branches communicate epigastric
side just superior to the inguinal ligament. The inferior with the superficial circumflex iliac, inferior epigastric, artery
epigastric artery runs superiorly toward the umbilicus, iliolumbar, and superior gluteal arteries. Femoral
supplying blood to the nearby peritoneum, transversalis artery
fascia, and rectus sheath. It has several branches that The final three arteries that supply blood to the Superficial
supply the abdominal muscles and overlying subcutane- abdominal wall are branches of the femoral artery. external
ous tissue and skin. Typically it anastomoses heavily The superficial epigastric artery passes superiorly across pudendal
with the superior epigastric and lower intercostal arter- the inguinal ligament and courses toward the umbilicus, artery
ies. Shortly after its origin, the inferior epigastric artery supplying the superficial inguinal lymph nodes as well Deep
releases the cremasteric artery and a small pubic artery. external
The latter artery anastomoses with a branch of the pudendal
obturator artery to supply structures on the posterior artery
aspect of the pubic bone. The cremasteric artery
accompanies the spermatic cord to supply the cremas- as the skin and the subcutaneous tissue of the medial,
teric muscle and fascia, ultimately anastomosing with lower abdomen. The superficial circumflex iliac artery
the testicular artery. In the female, this artery accom- courses anterior to and parallel with the inguinal liga-
panies the round ligament. ment (after piercing the fascia lata), providing blood to
the upper thigh and lateral side of the abdomen. The
The deep circumflex iliac artery courses in a sheath external pudendal artery emerges through the fossa ovalis
formed by the union of the transversalis and iliac fasciae and travels medially across the spermatic cord or round
(or between the latter and the peritoneum) laterally ligament to supply the skin and subcutaneous tissue in
and superiorly toward the anterior superior iliac spine. the suprapubic region. One branch anastomoses with
After piercing the transversalis fascia along the inner the dorsal artery of the penis or clitoris.
lip of the iliac crest, it continues to the crest’s midpoint
and passes through the transverse abdominal muscle
to pursue a posterior course between this and the inter-
nal abdominal oblique muscle. An ascending branch,

34 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-34  Overview of Upper Digestive Tract

VEINS OF ANTERIOR ABDOMINAL WALL

Axillary vein Subclavian vein Cephalic vein
Cephalic vein

Venous Drainage of
the Abdomen

The main collecting vessels of the abdomen are the Intercostal Axillary vein
inferior vena cava and the hepatic portal vein. The tributaries to Lateral
hepatic portal vein drains to the liver and it originates axillary vein thoracic vein
from smaller veins that drain the alimentary tract, its Areolar venous
associated glands, and the spleen. Here we will focus on Lateral plexus
the inferior vena cava and its tributaries, starting with thoracic vein Perforating
the superficial veins that drain the anterolateral abdom- Anterior tributaries to
inal wall. Please note that these veins accompany the intercostal veins internal thoracic
arteries of the same name, mostly in duplicate (venae Internal vein
comitantes) on both sides of the artery, being enwrapped thoracic vein
in the same sheath. Musculophrenic Thoraco-
vein epigastric vein
The external pudendal vein, aside from branches origi-
nating from the region above the symphysis pubis, Superior Tributaries of
receives the venous blood from the external genitalia epigastric veins paraumbilical
(superficial dorsal vein of the penis or clitoris and the sub- veins
cutaneous veins of the scrotum or labia majora), and joins, Thoraco- Thoraco-
in many instances, the great saphenous vein or the femoral epigastric vein epigastric vein
vein. The superficial epigastric and superficial circumflex Superficial
iliac veins, draining the medial and lateral parts of the Paraumbilical veins in epigastric vein
lower abdominal wall, respectively, pass superficial to round ligament of liver Superficial
the inguinal ligament and, piercing the cribriform circumflex
fascia, enter the femoral vein (in other instances, the Tributaries to deep iliac vein
great saphenous vein). In the body’s midaxillary line circumflex iliac veins External
the superficial veins of the upper and lower halves of pudendal vein
the trunk communicate through the thoracoepigastric Inferior
veins, which unite in the axilla with the lateral thoracic epigastric veins Cribriform
veins, each a branch of an axillary vein. This system of Superficial fascia over
anastomosis plays an important role in the event of an circumflex saphenous
obstruction of the superior or inferior vena cava. The iliac vein opening
thoracoepigastric veins receive numerous tributaries Great
from the surrounding superficial fascia as well as veins Thoraco- saphenous vein
emerging from the lateral aspect of the mammary epigastric Anterior
gland. vein (cut) scrotal veins
Superficial
Another collateral venous circulation of clinical sig- epigastric vein
nificance comes about through the superficial supraum-
bilical and infraumbilical veins, which, by means of five Saphenous opening
or six paraumbilical veins arising from the integument Femoral vein
and the musculoaponeurotic structures or the abdomi- External
nal wall, course within the ligamentum teres and enter pudendal vein
the left branch of the portal vein. When portal venous
pressure rises in liver cirrhosis, the paraumbilical veins Great saphenous vein
establish collaterals with the superior and inferior Pampiniform (venous) plexus
epigastric and thoracoepigastric veins, and become Superficial dorsal vein of penis
enlarged and tortuous, assuming a radial pattern known
as the caput medusae (head of Medusa). The internal iliac vein collects the blood from all Many of these vessels have their origins in a rich venous
pelvic structures, except the upper part of the rectum plexus, such as the pudendal, urethrovesical, and utero-
The two deeper veins that drain the anterolateral and the sigmoid colon, which drain to the portal system vaginal plexuses.
abdominal wall are the inferior epigastric and deep circum- via the inferior mesenteric vein, and the ovaries and
flex iliac veins, both of which enter the external iliac vein testes, which reach the inferior vena cava directly via The common iliac veins continue along the course of
(the continuation of the femoral vein) after having the gonadal veins. Starting near the superior part of the the external iliac veins in a median direction until the
drained the same regions supplied by the corresponding greater sciatic foramen and ascending over the piriform left vein meets the right vein, marking the starting point
arteries. This network of anastomoses, including the and psoas major muscles, the internal iliac vein receives of the inferior vena cava. The left common iliac vein,
musculophrenic and superior epigastric veins, likewise the superior and inferior gluteal, internal pudendal, obtura- often somewhat longer than its right counterpart,
conforms to the location of the arteries. The external tor, lateral sacral, middle rectal, and superior vesical veins. receives the middle sacral vein when this unpaired
iliac vein, beginning posterior to the inguinal ligaments, vessel does not enter (as it does frequently) the angle of
courses with its homonymous artery superiorly along
the brim of the lesser pelvis to unite with the internal
iliac vein anterior to the sacroiliac joint to form the
common iliac vein.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 35

Plate 1-35  Upper Digestive Tract: PART I

VEINS OF POSTERIOR ABDOMINAL WALL

Inferior vena cava Inferior phrenic veins Diaphragm Hepatic veins
Right inferior suprarenal vein Esophagus
Venous Drainage of the Left suprarenal veins and
Abdomen (Continued) Right renal vein anastomosis with inferior
Psoas major phrenic vein
the two iliac veins. Both common iliac veins receive the muscle (cut) Left renal vein
iliolumbar veins and, in some instances, the lateral sacral Ovarian
veins, if the latter have not entered the internal iliac Quadratus (testicular)
vein or have not joined the fifth lumbar vein. lumborum veins
muscle Ascending
The inferior vena cava commences at the right of L5, lumbar veins
ascends along the aorta anterior to the vertebral column, Subcostal Common
and continues posterior to the liver in a groove between vein iliac vein
the bare area and the caudal lobe. Immediately after the
inferior vena cava receives the three hepatic veins 1st to Internal iliac
(draining the liver), the inferior vena cava leaves the 4th right vein
abdomen through the diaphragm’s caval hiatus in the lumbar
central tendon. Because the caval hiatus lies superior to veins Superior
the aortic hiatus and the union of the two common iliac gluteal vein
veins is inferior to the aortic bifurcation, the inferior Iliolumbar
vena cava in the abdomen is about 7 to 8 cm longer vein Inferior
than the abdominal aorta. The first veins to enter the gluteal vein
inferior vena cava are the lumbar veins. The lowest Common Internal
(fifth) lumbar vein empties to the iliolumbar vein, iliac vein pudendal
whereas the upper four lumbar veins, lying on the Ovarian vein
bodies of the vertebrae and accompanying the arteries, (testicular)
drain into the posterior wall of the inferior vena cava veins and External
but may drain to the azygos or hemiazygos veins. The ureter iliac vein
connections that the lumbar veins make with the renal, (cut)
suprarenal, gonadal, deep circumflex, iliac, and other Internal Middle
abdominal veins are manifold. The most important iliac rectal vein
concerns the longitudinal anastomosis effected through vein
the ascending lumbar veins. These veins, beginning in the Median Uterine
pelvis as a continuation of the lateral sacral veins, sacral vein
ascend deep in the sulcus between the tendinous origins vein
of the psoas major muscle and the bodies and transverse Lateral Superior
processes of the vertebrae; after receiving branches sacral vesical vein
from the lumbar veins, the right ascending lumbar vein veins Obturator
drains into the azygos and the left into the hemiazygos, vein
or sometimes into the left renal vein. Posteriorly, the Deep
ascending lumbar veins make numerous connections circumflex
with the valveless veins of the vertebral venous system iliac vein
and thus bring the caval system into relationship with
the veins of the spine, spinal cord, dura mater, verte- Deep Round
brae, and brain. These relationships provide an expla- circumflex iliac vein ligament
nation for the spread of infections, tumors, and thrombi of uterus
from the pelvis, abdomen, or thorax into the central Rectal
nervous system, or bones of the skull and spine. venous
plexus
The right gonadal (testicular or ovarian) vein enters the Inferior
inferior vena cava superior to the lumbar veins, whereas epigastric vein
the left gonadal vein usually merges with the left renal
vein, or possibly the suprarenal vein, or one of the Superficial Uterovaginal
lumbar veins. The testicular veins, starting from the circumflex iliac vein venous plexus
pampiniform plexus in the spermatic cord, ascend along
the ductus deferens, pass through the inguinal canal, Superficial epigastric vein (cut)
and, following the artery, course superiorly on the psoas
Inferior epigastric vein (cut) Vesical venous plexus
Anterior abdominal
Femoral vein wall (turned down)
Pubic (obturator anastomotic) vein

Great saphenous vein

External pudendal vein

major muscle. The ovarian veins, derived from the and, occasionally, right renal vein. The left suprarenal
uterovaginal and ovarian plexuses, take a similar course. vein typically drains into the left renal or inferior
phrenic vein.
The large renal veins lie anterior to the corresponding
arteries and show much less variation than the renal Superior to the hepatic veins are the uppermost
arteries. The right renal vein rarely receives tributaries, tributaries of the inferior vena cava, the inferior phrenic
whereas on the left side, supernumerary veins such veins, which generally follow the course of the homony-
as the left gonadal and suprarenal veins typically join mous arteries. The left one may join the left renal vein
the vessel. The right suprarenal vein usually terminates separately or via a common trunk with the left supra-
with a direct connection with the inferior vena cava renal vein (5%).

36 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-36  Overview of Upper Digestive Tract
Thoracic duct
Right subclavian trunk
Tracheobronchial
nodes

Lymph Drainage of Thoracic duct Inferior phrenic
the Abdomen Cisterna chyli nodes
Right lumbar
The major lymphatic channels of the posterior abdomi- trunk Celiac
nal wall are essentially located along the large blood Intestinal trunk nodes
vessels. Thus the external iliac lymph vessels, interrupted Left lumbar trunk Superior
by nodes of the same name, course with the external iliac mesenteric
arteries and veins. Entering the pelvis posterior to the Common nodes
inguinal ligament about midway between the anterior iliac nodes Inferior
superior spine of the ilium and symphysis pubis, these Middle mesenteric
vessels receive lymph from the deep (and thereby also sacral nodes node
superficial) inguinal lymph nodes, through which pass the Lateral Visceral (preaortic)
lymphatic drainage of the lower extremities, the infe- sacral lymph nodes
rior parts of the anterolateral abdominal wall, and the nodes
perineum (including the external genitalia and anal Inferior Lumbar nodes
region). The internal iliac lymph vessels run, interrupted epigastric (lateral aortic
by the internal iliac nodes, with the artery and vein of the node nodes)
same name and drain the larger part of the organs and
wall of the true pelvis, whereas the remaining part of Deep Common
this region releases lymph through the presacral lym- inguinal iliac nodes
phatics. The external and internal iliac lymphatics join nodes
to form common iliac lymph vessels and nodes of the same Internal
name. Common iliac lymph vessels also receive input iliac nodes
from the presacral lymphatics with their lateral and
middle sacral nodes. The latter are situated in the retro- External
rectal connective tissue over the anterior surface of the iliac nodes
sacrum. In the region of the aortic bifurcation, the
common iliac lymph vessels proceed superiorly along Superficial
the lateral walls of the aorta to become the right and left inguinal
lumbar trunks. These trunks and the interposed lateral nodes
aortic lymph nodes receive afferents from the kidney and (superior,
the visceral (preaortic) lymph nodes. The extremely large horizontal,
area of drainage that the lumbar trunks serve includes, and
thus, the walls and organs of the lower abdomen as well inferior
as of the lower extremities. [vertical]
groups)
Both lumbar trunks unite in the region of the aortic
hiatus, anterior to the vertebral column (in the majority Node of Cloquet, or Rosenmüller
of cases), at the level of the upper third of L1 and the (highest deep inguinal node)
intervertebral disc between vertebrae T12 and L1, to
form the beginning of the thoracic duct. In about 50% thoracic vertebra, the thoracic duct draws away from this angle. At its point of entry into the veins, the tho-
of individuals, the thoracic duct starts with a distinctive, the spinal column in an anterior direction and proceeds racic duct does not always form a single entity but
elongated, saccular dilatation (≈ 1 to 1.5 cm in diameter between the left common carotid artery and the left sometimes divides into a triangular structure composed
and 5 to 7 cm in length), the cisterna chyli. Its three main subclavian artery, through the superior thoracic aper- of two or more branches. During its passage through
roots are the single intestinal trunk and the two lumbar ture, and into the left supraclavicular fossa. Here it the thorax, the thoracic duct is joined by vessels con-
trunks; however, two smaller tributaries coming from a arches superior to the subclavian artery and opens necting with the posterior parietal, tracheobronchial,
cranial direction and descending through the aortic either into the angle at which the left jugular and left and posterior mediastinal lymph nodes, as well as
hiatus of the diaphragm also join the cisterna chyli. subclavian veins join to form the left brachiocephalic smaller lymph vessels draining the thoracic wall and
vein or, less often, into one of the two veins forming thoracic organs.
The thoracic duct passes first to the right across the
posterior surface of the aorta, through the aortic hiatus
of the diaphragm into the mediastinum, ascending
between the aorta and the azygos vein, anterior to the
lower thoracic vertebrae and right intercostal arteries.
On reaching the level of the fifth thoracic vertebra,
it courses posterior to the esophagus to the left side of
the spinal column, where it runs for a short distance to
the right of the aorta and then crosses posterior to the
aortic arch to continue its ascent. Opposite the third

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 37

Plate 1-37  Upper Digestive Tract: PART I

Spinal nerve THORACOABDOMINAL NERVES
Recurrent meningeal nerve Anterior (ventral) ramus of spinal nerve
(intercostal nerve)
Spinal sensory
(posterior root) ganglion Erector spinae muscle Collateral branch

Posterior (dorsal) root Medial branch, External intercostal muscle
Anterior (ventral) Lateral branch of
root Posterior Internal intercostal muscle
(dorsal) Innermost intercostal muscle
ramus Subcostal muscles
Latissimus dorsi muscle
Serratus
anterior
muscle

Innervation of Abdomen
and Perineum

The segmentally arranged nerves are attached to the Window cut
sides of the spinal cord by a series of anterior (ventral) in innermost
and posterior (dorsal) roots. An anterior and posterior root intercostal muscle
at each spinal segment unite to form the spinal nerve,
which emerges through the corresponding interverte- Communicating Internal
bral foramen. The anterior roots contain axons from branch intercostal
the motor nerve cells in the anterior horn of the spinal muscle
cord and the posterior roots contain the axons project- Internal intercostal
ing from the pseudounipolar sensory cells located in the membranes anterior
posterior (dorsal) root ganglia (spinal sensory ganglia). Greater and lesser to external Collateral branch
splanchnic nerves intercostal muscles rejoining intercostal nerve
The spinal nerve only exists for a short span before
dividing into anterior and posterior rami, each of which Sympathetic trunk Innermost intercostal muscle
carries both motor and sensory axons to their target Gray and white
tissues. Before splitting into rami, each of the spinal rami communicantes Internal intercostal muscle
nerves gives off a small recurrent meningeal branch that External intercostal muscle
is sensory to the nearby spinal dura mater and interver-
tebral disc. After emerging from the intervertebral Transversus abdominis muscle External intercostal
foramen, each spinal nerve receives a branch or branches Rectus abdominis muscle membrane
(gray rami communicantes) from an adjacent ganglion of
the sympathetic trunk, which contains postganglionic Linea alba Lateral
sympathetic axons originating from the cells of that cutaneous
ganglion. Of the first thoracic through the first two or, branch
occasionally, three lumbar anterior rami, each contrib-
utes a branch or branches (white rami communicantes), External
which contain preganglionic sympathetic fibers to the oblique
corresponding sympathetic ganglia. muscle
Anterior
In general, the posterior rami are smaller than the cutaneous
anterior rami and do not unite to form plexuses. They branch
divide into medial and lateral branches that supply the
muscles and skin of the back. The anterior rami supply nerve innervates the skin at the level of the nipple. The lateral cutaneous branch. The former, separating from the
the anterolateral aspects of the trunk as well as the lower five pairs of intercostal nerves and the subcostal primary ramus only a few centimeters away from the
limbs. In the cervical, lumbar, sacral, and coccygeal nerves supply the thoracic and abdominal body wall and vertebrae, inclines inferiorly from the parent nerve, runs
regions, the anterior rami converge to form plexuses, also contribute fibers to the diaphragm. along the lower border of the intercostal space, and ends
but in the thoracic region, they maintain their segmen- anteriorly as a small cutaneous nerve. The lateral cuta-
tal character and each runs separately and indepen- Typically, the 7th to 11th intercostal nerves course neous branch accompanies the main intercostal nerve
dently to the site or structure it innervates. anteriorly along the thoracic wall below the correspond- as far as the midaxillary line before piercing the inter-
ing rib and intercostal vessels. Posteriorly, the nerve lies costal muscles and dividing into anterior and posterior
The thoracic anterior rami, the intercostal nerves, are between the pleura and the posterior intercostal membrane branches, which are mainly cutaneous in distribution.
distributed chiefly to the anterolateral walls of the and passes between the internal and innermost intercostal The intercostal nerves supply intercostal, subcostal, and
thorax and abdomen. They are 12 in number on each muscles. Each nerve gives off a collateral branch and a
side, but only 11 are truly intercostal. The 12th pair lie
below the last ribs and are termed subcostal nerves. The
upper six pairs of intercostal nerves are limited in their
supply to the thoracic body wall, although the first and
second intercostal nerves also contribute to the brachial
plexus, the innervation of the upper limbs. The fourth

38 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-38  Overview of Upper Digestive Tract
NERVES OF ANTERIOR ABDOMINAL WALL

1

2 2

Medial brachial 3 3
cutaneous nerve 4
Intercosto- 5 4
brachial 6
Innervation of Abdomen and nerve (T1, 2) 7 5 Serratus
Perineum (Continued) Long 8 6 anterior muscle
thoracic nerve
transverse thoracic muscles. The lower five or six inter- Latissimus 9 External oblique
costal nerves also supply sensory axons to the peripheral dorsi muscle 10 muscle (cut)
parts of the diaphragm. Lateral cutaneous 7 Posterior layer
branches of 11 of rectus sheath
The lower five intercostal nerves and the subcostal intercostal
nerves pass posterior to the costal cartilages and enter nerve (T2–11) Anterior layer
the abdominal wall to supply the external and internal Anterior cutaneous of rectus
abdominal oblique, transversus abdominis, and rectus branches of 8 sheath (cut)
abdominis muscles and end as anterior abdominal cutane- intercostal
ous branches. The 10th nerve serves the dermatome at nerve (T1–11) Transversus
the level of the umbilicus. The lateral cutaneous branch Lateral cutaneous abdominis muscle
of the subcostal nerve (T12) pierces the internal and branch of subcostal
external oblique abdominal muscles and descends over nerve (T12) 9 Internal oblique
the iliac crest to assist in supplying the skin over the Lateral cutaneous muscle and
upper lateral part of the thigh. branch of iliohypo- aponeurosis (cut)
gastric nerve (L1)
The anterior rami of the lower spinal nerves (five 10 Anterior and
lumbar, five sacral, and one coccygeal) divide and Anterior cutaneous lateral cutaneous
reunite in a plexiform fashion to form the lumbar, sacral, branch of subcostal branches of sub-
and coccygeal plexuses. They are interconnected as nerve (T12) costal nerve (T12)
described above with the sympathetic trunks via rami Lateral femoral
communicantes. cutaneous 11 Anterior branch
nerve (L2, 3) of iliohypogastric
The lumbar plexus is formed by the anterior rami of nerve (L1)
the first three lumbar nerves and the greater part of the Femoral branches
fourth lumbar nerve, along with a contribution from of genitofemoral Ilioinguinal
the subcostal nerve. It is situated anterior to the lumbar nerve (L1, 2) nerve (L1)
vertebral transverse processes and is embedded in the Anterior cutaneous
posterior part of the psoas major muscle, which needs branch of iliohypo- External oblique
to be dissected to make the plexus accessible. The most gastric nerve (L1) aponeurosis (cut)
common course and distribution of the components of
the plexus and its relationship are described and illus- Anterior scrotal Ilioinguinal
trated here, but it should be kept in mind that variations branch of ilio- nerve (L1)
of the lumbar plexus are frequent. inguinal nerve (L1)
Cremasteric
The first lumbar nerve, after receiving a twig from Genital branch of muscle of
the subcostal nerve, splits into an upper branch and a genitofemoral spermatic cord
smaller lower branch. The former divides into the ilio- nerve (L1, 2)
hypogastric and ilioinguinal nerves, and the latter unites Anterior cutaneous branch
with a twig of the second lumbar nerve to form the of iliohypogastric nerve (L1)
genitofemoral nerve. The rest of the second lumbar External spermatic fascia of spermatic cord
nerve, the third, and that part of the fourth which con- Rectus abdominis muscle
tributes to this plexus, each divide also into anterior and
posterior sections, which combine to constitute the Muscular branches from the subcostal and upper four collateral branch of an intercostal nerve. The former
obturator and femoral nerves, respectively. The accessory lumbar nerves supply the quadratus lumborum muscle, nerve gives off a lateral branch, which crosses the iliac
obturator nerve, when present, is formed by branches and those of the first and second reach the psoas major crest a short distance posterior to the corresponding
from the anterior divisions of the third and fourth and psoas minor muscles. The psoas major muscles are branch of the subcostal nerve, both nerves supplying
nerves, whereas the lateral femoral cutaneous nerve further innervated by branches from the third and, skin of the superior lateral part of the thigh. Continuing
evolves by the fusion of small offshoots from the pos- sometimes, fourth lumbar nerves, which also supply the anteriorly, the anterior branch of the iliohypogastric nerve
terior divisions of the second and third lumbar nerves. iliacus muscles. sends filaments to the transverse and oblique abdominal
muscles, pierces the external oblique aponeurosis about
The iliohypogastric and ilioinguinal nerves resemble the 3 cm superior to the superficial inguinal ring, and ter-
thoracic nerves in their course and distribution, being minates innervating the skin just superior to the pubis.
analogous, respectively, to the main trunk and the

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 39

Plate 1-39  Upper Digestive Tract: PART I

Intercostal nerve (T11) LUMBOSACRAL AND COCCYGEAL PLEXUSES Anterior
T12 division
Subcostal nerve (T12) Posterior
Rami L1 division
Iliohypogastric nerve communicantes
(L1) Sympathetic
Ilioinguinal trunk
nerve (L1)
To psoas major
and psoas minor
muscles
Genitofemoral
nerve (L1, 2)

Innervation of Abdomen and Lateral femoral cuta- L2
Perineum (Continued) neous nerve (L2, 3) Lumbar
Genital branch (L1) plexus
The ilioinguinal nerve supplies filaments to the adja- and Femoral
cent muscles and, after piercing the same muscles as the branch (L2) L3
iliohypogastric nerve, enters the inguinal canal, runs of genitofemoral
deep to the spermatic cord, and emerges through the nerve
superficial inguinal ring to supply the superior medial To psoas major
side of the thigh, the root of the penis, and the anterior and iliacus
part of the scrotum in the male, and the mons pubis and muscles
labium majora in the female.
Anterior L4
The genitofemoral nerve, after emerging from the branches L5
lumbar plexus, passes through the psoas major muscle and Lateral
and descends on its anterior surface, deep to the peri- branches of
toneum, to divide into the genital and femoral branches subcostal and
at about the level of the fifth lumbar vertebra. The iliohypogastric
former branch enters the inguinal canal through the nerves
deep inguinal ring, innervates the cremaster muscle, Lumbosacral
and contributes some twigs to the skin of the scrotum, trunk
or the labium majora of the female. The femoral branch
runs lateral to the external iliac and femoral arteries, Nerve to S1 Sacral
passes posterior to the inguinal ligament, and, after quadratus plexus
piercing the anterior layer of the femoral sheath and femoris (and
the fascia lata, ramifies in the superficial tissues and skin inferior gemellus) S2
over the femoral triangle. The genitofemoral nerve and (L4, 5, S1)
its branches carry many of the efferent and afferent
fibers to and from the common iliac, external iliac, and Nerve to obturator S3 Coccygeal
femoral arteries. internus (and superior plexus
gemellus) (L5, S1, 2) S4 Pelvic splanchnic
Other branches of the lumbar plexus (e.g., the femoral Superior gluteal nerve (L4, 5, S1) S5 nerves (parasym-
nerve), except for muscular rami to the quadratus lum- Co pathetics)
borum, psoas major, and iliacus muscles, are distributed Nerve to piriformis (S1, 2) Perforating
to the lower limb and, consequently, are not discussed Obturator nerve (L2, 3, 4) cutaneous
in this volume. Accessory nerve (S2, 3)
obturator nerve Nerve to levator
The anterior rami of the sacral and coccygeal nerves, (L3, 4) ani and coccygeus
which, in contrast to the lumbar nerves, diminish in size (inconstant) (S3, 4)
as they progress inferiorly, divide and reunite to con- Femoral nerve
tribute to the sacral and coccygeal plexuses. These lie on (L2, 3, 4)
the posterior wall of the pelvis, posterior to the ureters, Inferior gluteal
internal iliac vessels, and intestinal coils, and anterior nerve (L5, S1, 2)
to the piriformis and coccygeus muscles. The inferior
and smaller part of the fourth lumbar nerve unites with Sciatic nerve Perineal branch of
the anterior ramus of the fifth lumbar nerve as the 4th sacral nerve
lumbosacral trunk, which, together with the anterior Posterior femoral
rami of the first three and the upper part of the fourth cutaneous nerve Anococcygeal
sacral nerves, constitutes the sacral plexus. The lower (S1, 2, 3) nerves
part of the fourth sacral joins the fifth sacral and coc- Pudendal nerve (S2, 3, 4) Obturator nerve
cygeal nerves to form the small coccygeal plexus. Inferior anal (rectal) nerve
Sciatic Common fibular Dorsal nerve of penis/clitoris
Each nerve entering into the composition of these nerve (peroneal) nerve (L4, 5, S1, 2)
two plexuses receives postganglionic sympathetic fibers Perineal nerve and Posterior scrotal/labial branches
by way of one or more gray rami communicantes from Tibial nerve (L4, 5, S1, 2, 3) Posterior femoral cutaneous nerve
an adjacent ganglion of the sympathetic trunk. Pregan-
glionic parasympathetic fibers originate in the second piriformis muscle. This large nerve consists of a tibial
to fourth sacral levels of the spinal cord; they emerge section and a common fibular section, which usually remain
with the second, third, and fourth sacral nerves and fused until about the lower third of the thigh, but which
leave thereafter as pelvic splanchnic nerves. may occasionally be separated at their points of origin
or may divide before the nerve leaves the pelvis. The
The sacral plexus, by convergence and fusion of its nerve of the sacral plexus splits into anterior and pos-
roots, develops into a flattened band, from which many terior divisions, which, in some individuals, unite again
branches arise, before the large sciatic nerve passes to produce the nerves. Most branches of the sacral
through the greater sciatic foramen inferior to the

40 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS

Plate 1-40  Overview of Upper Digestive Tract

NERVES OF POSTERIOR ABDOMINAL WALL
Greater, lesser, and least Iliohypogastric nerve (L1)
splanchnic nerves
Ilioinguinal nerve (L1)
Sympathetic trunks
Celiac, superior mesenteric, Muscular branches from lumbar plexus
Iliohypogastric nerve (L1) and aorticorenal ganglia
Subcostal nerve (T12)
Subcostal nerve (T12)
Psoas major muscle (cut)

Genitofemoral Quadratus
nerve (L1, 2) lumborum muscle

Ilioinguinal Iliohypo-
nerve (L1) gastric
nerve
(L1)

Ilio-
inguinal
nerve
(L1)

Innervation of Abdomen and Transversus Genito-
Perineum (Continued) abdominis femoral
muscle nerve
plexus supply the lower limb and will be discussed in (cut) (L1, 2)
the volume addressing the musculoskeletal system. Subcostal Gray
Others are distributed in the pelvic and perineal regions. nerve (T12) and
and its white
The nerves to the piriformis, levator ani, and coccygeus lateral rami
muscles pierce the anterior or pelvic surfaces of these cutaneous com-
muscles. The nerve to the obturator internus muscle (not branch muni-
to be confused with the obturator nerve) leaves the Gray rami cantes
pelvis through the greater sciatic foramen inferior to communi-
the piriformis muscle, crosses the ischial spine lateral to cantes Lateral
the pudendal nerve and internal pudendal vessels, reen- Lateral femoral
ters the pelvis through the lesser sciatic foramen, and femoral cuta-
sinks into the pelvic surface of the obturator internus cutaneous neous
muscle. nerve nerve
(L2, 3) (L2, 3)
The pudendal nerve passes between the piriformis and Intermes-
coccygeus muscles, leaves the pelvis through the greater Femoral nerve (L2–L4) enteric
sciatic foramen, alongside the sciatic nerve, crosses pos- (para-
teroinferior to the ischial spine (medial to the internal aortic)
pudendal artery), and accompanies that vessel through plexus
the lesser sciatic foramen into the pudendal canal on Femoral
the obturator internus fascia. As the nerve enters the branch,
canal, it gives off the inferior rectal nerve and shortly Genital branch
thereafter terminates by splitting into the perineal of genitofemoral
nerve and the dorsal nerve of the penis or clitoris, nerve (L1, 2)
respectively. Femoral nerve
Lumbosacral
The inferior rectal nerve perforates the medial wall trunks (L4, 5)
of the pudendal canal, crosses the ischioanal fossa
obliquely with the inferior rectal vessels, and divides Obturator nerves
into branches that are the main supply of the external Accessory obturator
anal sphincter, the lining of the lower part of the anal nerve (L3, 4) (occasional)
canal, and the skin around the anus. Its branches com- Lumbosacral plexus (L4–S4)
municate with the perineal branches of the posterior
femoral cutaneous, fourth sacral, and perforating cuta- Pudendal nerve (S2, 3, 4)
neous nerves and the perineal nerve, which is the larger Obturator nerve (L2, 3, 4)
terminal branch of the pudendal nerve. This latter Anterior cutaneous branch of
nerve runs anteriorly in the pudendal canal inferior to iliohypogastric nerve (L1)
the internal pudendal artery, projecting toward the pos- Anterior scrotal (labial) branches of
terior border of the urogenital diaphragm, near which ilioinguinal nerve (L1)
it divides into superficial and deep branches. The super-
ficial one divides into medial and lateral posterior scrotal Genital branch of genitofemoral nerve (L1, 2)
(or labial) nerves, which spread over the skin of the Femoral branches
scrotum or labia majora, communicating with the
perineal branch of the posterior femoral cutaneous spongiosus muscle and is distributed to the erectile the nerve comes to lie alongside the dorsal artery of the
nerve. The deep branches supply the anterior parts of tissue of the corpus spongiosum and the mucous mem- penis and continues as far as the glans and the prepuce.
the external anal sphincter, the superficial and deep brane of the urethra. In the female the dorsal nerve of the clitoris is smaller,
transverse perineal, bulbospongiosus, and ischiocavernosus but its distribution is similar.
muscles, as well as the sphincter urethrae (and, in a The dorsal nerve of the penis accompanies the internal
subsidiary fashion, the levator ani). A twig, termed the pudendal artery in its course through the deep transver- The posterior femoral cutaneous nerve, besides inner-
nerve of the bulb, arises from the branch to the bulbo- sal perineal muscle and passes anterior to the pubic arch vating the skin of the posterior thigh, gives off a gluteal
under cover of the ischiocavernosus muscle and corpus branch, the inferior cluneal nerve, supplying the skin
cavernosum penis. Passing through a gap between the area over the lower part of the gluteus maximus and,
inferior fascia and the apex of the urogenital diaphragm, in the same region, a perineal branch that curves

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 41