Part 3. Skeletal Muscles of the Human Body
Insertion: decreases the pressure within the thoracic cavity,
Central tendon (trifoliate-shaped) of diaphragm forcing air into the lungs through the open glottis
immediately below the pericardium and blending by the higher pressure of the atmospheric air.
with it. The central tendon has no bony These events occur along with intercostal muscle
attachments. It has three divisions called leaflets action, which elevates the ribs, sternum, and
(because of its cloverleaf pattern) in an otherwise vertebrae, increasing the anteroposterior and
continuous sheet of muscle, which affords the transverse thoracic dimensions for the inspira-
muscle great strength. tory effort.
The diaphragm adds power to expulsive efforts:
Description: lifting heavy loads, sneezing, coughing, laugh
This half-dome-shaped muscle of contractile and ing, parturition, evacuation of bladder and
fibrous structure forms the floor of the thorax bowels. These activities are preceded by deep
(convex upper surface) and the roof of the inspiration.
abdomen (concave inferior surface) (Figure 9-4). Expiration: Passive relaxation allows the half-dome
The diaphragm is muscular on the periphery and to ascend, thus decreasing thoracic cavity volume
its central area is tendinous. It closes the open- and increasing its pressure.
ing of the thoracic outlet and forms a convex
floor for the thoracic cavity. The muscle is flat- Innervation:
ter centrally than at the periphery and higher Phrenic nerve, C4 (with contributions from C3 and
on the right (reaching rib 5) than on the left C5)
(reaching rib 6 ) . From the peak on each side,
the diaphragm abruptly descends to its costal The Intercostals
and vertebral attachments. This descending
slope is much more precipitous and longer The intercostal muscles are slim layers of muscle and
posteriorly. tendon occupying each of the intercostal spaces; the
externals are the most superficial with the internals
Function: underneath them, and the deepest are the intimi.
Inspiration: Contraction of the diaphragm with the
lower ribs fixed draws the central tendon 102 EXTERNAL INTERCOSTALS
downward and forward during inspiration. This
increases the vertical thoracic dimensions and (Intercostales Externi)
pushes the abdominal viscera downward. It also
11 pairs of muscles
FIGURE 9-4 The diaphragm.
Origin:
Ribs 1 to 11 (lower borders and costal tubercles)
Superior costotransverse ligaments
Insertion:
Ribs 2 to 12 (upper border of rib below)
Aponeurotic external intercostal membrane
Sternum (via aponeurosis)
Description:
There are 11 of these muscles on each side of the
chest. Each arises from the inferior margin of one
rib and inserts on the superior margin of the rib
below. They extend in the intercostal spaces from
the tubercles of the ribs dorsally to the cartilages
of the ribs ventrally.
The muscle fibers run obliquely inferolaterally on the
dorsal thorax; they run inferomedially and
somewhat ventrally on the anterior thorax (down
and toward the sternum).
The externi are the thickest of the three intercostal
muscles. In appearance they may seem to be
continuations of the external oblique abdominal
muscles.
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Function: Innervation:
The muscles of respiration are highly coordinated T l - T l l intercostal nerves (ventral rami)
between abdominal and thoracic processes, with
the diaphragm being the major muscle of 104 INTERCOSTALES INTIMI
inspiration, accounting for about 2 / 3 of vital
capacity. The external intercostals are more active Origin:
in inspiration than expiration but work closely with Costal groove of rib above the rib of insertion;
the internal intercostals to stiffen the chest wall, found in lower costal interspaces when present,
preventing paradoxical motion during descent of but no consistent evidence in upper five to six
the diaphragm. interspaces
Elevation of ribs in inspiration. There are data to Insertion:
support this claim for the upper four or five Upper margin of the rib below the rib of origin;
muscles, but the more dorsal and lateral fibers found in lower costal interspaces
of the same muscles also are active in early ex-
piration. It is possible that the activity of the Description:
intercostals during respiration varies with the There is dispute about whether this is a separate
depth of breathing.17 muscle or just a part of the internal intercostals.
It is a thin sheet lying deep to the internal
Depression of the ribs in expiration (supporting data intercostals, but arguments in favor of a separate
sparse) muscle are not convincing. If they are separate,
there may be five to six pairs, with no consistent
Rotation of thoracic spine to opposite side presence in the upper costal interspaces.
(unilateral) Considered insignificant.
Stabilization of rib cage Function:
Presumed to be identical to intercostales interni
Innervation
T l - T l l intercostal nerves (ventral rami). Innervation: nerves (ventral rami)
These nerves are numbered sequentially according to T l - T l l intercostal
interspace; e.g., the 5 th intercostal nerve (inconsistent)
innervates muscle occupying the 5th intercostal
space between the 5th and 6th ribs. 105 SUBCOSTALES
103 INTERNAL INTERCOSTALS Origin:
Lower ribs (variable) on inner surface near angle
(Intercostales Interni)
Insertion:
Origin:
Ribs 1 to 11 (ridge on inner surface, then passing Inner surface of two or three ribs below rib of
down and toward spine) origin
Costal cartilage of same rib
Sternum (anterior) Description:
Upper border and costal cartilage of rib below Lying on the dorsal thoracic wall, these muscles are
Internal intercostal membrane (aponeurosis) discretely developed only in the lower thorax.
Fibers run in the same direction as those of the
Insertion: intercostales interni.
Ribs 2 to 12 (upper border of next rib below) Function:
Draws adjacent ribs together or depresses ribs (no
Description: supporting data)
There are 11 pairs of these muscles. They extend Innervation:
from the sternal end of the ribs anteriorly to the T 7 - T 1 1 intercostal nerves (ventral rami)
angle of the ribs posteriorly. The fibers run
obliquely downward but at a 90° angle to the 106 TRANSVERSE THORACIS
external intercostals.
Origin:
Function: Sternum (caudal 1/3; xiphoid, posterior surface)
Not as strong as the external intercostals Ribs 3 to 6 (costal cartilages, inner side)
Elevation of ribs in inspiration. This may be true
at least for the 1st to 5th muscles. The more
lateral muscle fibers run more obliquely inferior
and posterior and are most active in
expiration.17
Stabilization of rib cage
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Insertion: erector spinae and under the rhomboids. Fibers
run inferolaterally.
Ribs 2 to 5 (costal cartilages, caudal borders)
Function: volume (function
Description: Elevates upper ribs (debated)
A thin plane on the inner surface of the anterior Presumably increases thoracic
wall of the thorax. The fibers pass obliquely up uncertain)
and laterally, diverging more as they insert. The
lowest fibers are horizontal and are continuous Innervation:
with the transversus abdominis. The highest fibers T 2 - T 5 spinal nerves (ventral rami)
are almost vertical. Attachments vary from side to
side in the same person and among different 109 SERRATUS POSTERIOR INFERIOR
persons.
Origin:
Function: T 1 1 - T 1 2 and L 1 - L 2 vertebrae (spinous processes via
Draws ribs downward; narrows chest thoracolumbar fascia)
Active in forced expiration Supraspinous ligaments
Innervation: Insertion:
T 2 - T 1 1 intercostal nerves (ventral rami) Ribs 9 to 12 (inferior borders, lateral to angles)
107 LEVATORES COSTARUM Description:
12 pairs of muscles A thin muscle, composed of four digitations, lying
at the border between the thoracic and lumbar
Origin: regions. Fibers ascend laterally. It is much broader
than the serratus posterior superior and lies four
C7 and T l - T l l vertebrae (transverse processes) ribs below it. It lies over the erector spinae and
under the latissimus dorsi.4 The muscle may have
Insertion: fewer than four digitations, or digitations may be
Rib immediately below rib of origin (upper margin, absent.
outer edge between angle and tubercle)
Function:
Description: Depresses lower ribs and moves them dorsally
There are 12 pairs of these muscles on either side of Has an uncertain role in respiration
the thorax on its posterior wall. Fibers run
obliquely inferolaterally, like those of the external Innervation:
intercostal muscles. The most inferior fibers divide T 9 - T 1 2 spinal nerves (ventral rami)
into two fasciculi, one of which inserts as
described; the other descends to the second rib Muscles of the Abdomen
below its origin.
Anterolateral Walls
Function:
Elevation of ribs in inspiration (disputed) 110 Obliquus externus abdominis
Lateral bending of spine 111 Obliquus internus abdominis
112 Transversus abdominis
Innervation: 113 Rectus abdominis
T l - T l l intercostal nerves and sometimes C8 (dorsal 114 Pyramidalis
rami)
110 OBLIQUUS EXTERNUS
108 SERRATUS POSTERIOR SUPERIOR ABDOMINIS
Origin: Origin:
C7 and T 1 - T 3 vertebrae (spinous processes) Ribs 5 to 12 (by digitations that attach to the
Ligamentum nuchae external and inferior surfaces and alternate
Supraspinous ligaments with digitations of the serratus anterior and
latissimus dorsi)
Insertion:
Ribs 2 to 5 (upper borders, lateral to angles)
Description:
Muscle lies on the upper dorsal thorax, over the
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Part 3. Skeletal Muscles of the Human Body
Insertion: Aponeurosis that splits at the lateral border of the
Iliac crest (anterior half of outer lip) rectus abdominis to encircle the muscle and reunite
Iliac fascia at the linea alba
Aponeurosis from the prominence of the 9th costal
cartilage to anterior superior iliac spine (ASIS); Cartilages of ribs 7 to 9 (via an aponeurosis)
aponeuroses from both sides meet at the linea Pubis (crest and pecten pubis) from tendinous sheath
alba.
of transverse abdominis
Description:
The largest and most superficial flat, thin muscle Description:
of the abdomen curves around the anterior and
lateral walls. Its muscular fibers lie on the lat- This muscle is smaller and thinner than the exter-
eral wall while its aponeurosis traverses the an- nal oblique under which it lies in the lateral
terior wall in front of the rectus abdominis, and ventral abdominal wall. The fibers from the
meeting its opposite number to form the linea iliac crest pass upward and medially to ribs 9 to
alba. The digitations form an oblique line that 12 and the aponeurosis; the more lateral the
runs down and backward. The linea alba ex- fibers, the more they run toward the vertical.
tends from the xiphoid process to the symphysis The lowest fibers pass almost horizontally on
pubis. the lower abdomen.
The upper (superior) five digitations increase in size Function:
as they descend and alternate with the Flexion of spine (bilateral)
corresponding digitations of the serratus anterior. Lateral bending of spine (unilateral)
The distal three digitations decrease in size as they Rotation of trunk to same side (unilateral)
descend and alternate with digitations of the Increases abdominal pressure to assist in defecation
latissimus dorsi. The superior fibers travel and other expulsive actions
inferomedially; the posterior fibers pass more Forces viscera upward during expiration to elevate
vertically. diaphragm
Elevation of pelvis
Function: Innervation: ilioinguinal
Flexion of trunk (bilateral muscles) T 7 - T 1 2 spinal nerves (ventral rami)
Tilts pelvis posteriorly L1 spinal nerve (iliohypogastric and
Elevates pelvis (unilateral) branches) (ventral rami)
Rotation of trunk to opposite side (unilateral)
Lateral bending of trunk (unilateral) 112 TRANSVERSE ABDOMINIS
Support and compression of abdominal viscera,
counteracting effect of gravity on abdominal Origin:
contents Inguinal ligament (lateral 1/3)
Assists defecation, micturition, emesis, and parturi- Iliac crest (anterior 2/3 of inner lip)
tion (i.e., expulsion of contents of abdominal Thoracolumbar fascia (between iliac crest and 12th
viscera and air from lungs) rib)
Important accessory muscle of forced expiration
(during expiration it forces the viscera upward to Ribs 7 to 12 (costal cartilages)
elevate the diaphragm)
Insertion:
Innervation:
T 7 - T 1 2 spinal nerves (ventral rami) Pubis (crest and pecten pubis) via aponeurosis
along with aponeurosis of the internal oblique
111 OBLIQUUS INTERNUS to form the falx inguinalis
ABDOMINIS
Linea alba (upper and middle fibers pass medially
Origin: to blend with the posterior layer of the broad
Thoracolumbar fascia aponeurosis encircling the rectus abdominis)
Inguinal ligament (lateral 2/3 of upper aspect)
Iliac crest (anterior 2/3 of intermediate line) Description:
The innermost of the flat abdominal muscles, the
Insertion: cartilages by transversus abdominis lies under the internal
Ribs 9 to 12 (inferior borders and with internal oblique. Its name derives from the direction of
digitations that appear continuous its fibers, which pass horizontally across the lat-
intercostals) eral abdomen to an aponeurosis and the linea alba.
The length of the fibers varies considerably
depending on the insertion site, the most inferior
to the pubis being the longest. At its origin on
ribs 7 to 12, the muscle interdigitates with similar
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Part 3. Skeletal Muscles of the Human Body
diaphragmatic digitations separated by a narrow 114 PYRAMIDALIS
raphe.
Origin:
Function: Pubis (front of body and symphysis via ligamentous
Constricts (flattens) abdomen, compressing the fibers)
abdominal viscera and assisting in expelling their
contents Insertion:
Forced expiration
Linea alba (midway between umbilicus and pubis)
Innervation: ilioinguinal
T 7 - T 1 2 spinal nerves (ventral rami) Description
L1 spinal nerve (iliohypogastric and A small triangular muscle located in the extreme
branches) (ventral rami) distal portion of the abdominal wall and lying
anterior to the lower rectus abdominis. Its ori-
113 RECTUS ABDOMINIS gin on the pubis is wide, and it narrows as it
rises to a pointed insertion. The muscle varies
Origin: considerably from side to side and may be present
By two tendons inferiorly: or absent.
Lateral: Pubis (tubercle on crest and pecten pubis)
Medial: Ligaments covering front of symphysis Function:
pubis Tenses the linea alba
Insertion: Innervation:
Ribs 5 to 7 (costal cartilages by three fascicles of T 1 2 spinal nerve (subcostal nerve) (ventral ramus)
differing size)
Sternum (xiphoid process, costoxiphoid ligaments) Muscles of the Perineum
Description: 115 Levator ani
A long muscular strap extending from the ventral
lower sternum to the pubis. Its vertical fibers lie 116 Coccygeus
centrally along the abdomen, each separated
from its contralateral partner by the linea alba. 117 Cremaster
T h e muscle is interrupted (but not all the way
through) by three (or more) fibrous bands 118 Transversus perinei superficialis
called the tendinous intersections, which pass
transversely across the muscle in a zigzag fash- 119 Transversus perinei profundus
ion. The most superior intersection generally is
at the level of the xiphoid; the lowest is at the 120 Bulbospongiosus
level of the umbilicus, and the second intersec-
tion is midway between the two. These are 121 Ischiocavernosus
readily visible on bodybuilders or others with
well-developed musculature. 122 Sphincter urethrae
Function: 123 Sphincter ani externus
Flexion of spine (draws symphysis and sternum
toward each other) Corrugator cutis ani (involuntary muscle, not
Posterior tilt of pelvis described)
With other abdominal muscles, compresses
abdominal contents Internal anal sphincter (involuntary muscle, not
described)
Innervation:
T 7 - T 1 2 spinal nerves (ventral rami) 115 LEVATOR ANI
T7 innervates fibers above the superior tendinous
intersection; T8 innervates fibers between the Origin:
superior and middle intersections; T9 innervates Pubococcygeus part: Pubis (inner surface of superior
fibers between the middle and distal inter- ramus)
sections. Coccyx (anterior)
Blends with longitudinal rectus muscle and fascia
Puborectal part: Same origin as pubococcygeus but
splits off to join its opposite member, along with
sphincter externus, to form an anorectal sling
Iliococcygeus part: Ischium (inner surface of spine)
Iliosacralis part: Accessory slip
Obturator fascia
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Insertion: Innervation: nerves (pudendal plexus) (ventral
Coccyx (last two segments) S3-S4 spinal
Anococcygeal raphe rami)
Sphincter ani externus
117 CREMASTER
Description:
A part of the pelvic diaphragm, this broad, thin sheet Origin:
of muscle unites with its contralateral partner to Lateral part: Inguinal ligament (continuous with
form a complete pelvic floor. Anteriorly it is internal oblique and occasionally from transverse
attached to the pubis lateral to the symphysis, abdominis). Technically this is an abdominal
posteriorly to the ischial spine, and between these muscle.
to the obturator fascia. The fibers course medially Medial part: Pubis (crest, tubercle, and falx
with varying obliquity. inguinalis). This part is inconstant.
There are links to the sphincter urethrae, to the
prostate as the levator prostatae, to the Insertion:
pubovaginalis walls of the vagina in the female, Pubis (tubercle and crest)
and to the perineal body and rectum in both men Sheath of rectus abdominis and transversus
and women. In animals these parts are attached abdominis
to caudal vertebrae and control tail motions. Loss
of a tail in humans leaves these muscles to form Description:
a stronger pelvic floor. Consists of loose fasciculi lying along the sper-
matic cord and held together by areolar tissue
Function: to form the cremasteric fascia around the cord
Constriction of rectum and vagina contributing to and testis. Often said to be continuous with the
continence; they must relax to permit internal oblique abdominal muscle or with the
expulsion. transversus abdominis. After passage through
Along with the coccygei, the levator forms a muscular the superficial inguinal ring, the muscle spreads
pelvic diaphragm that supports the pelvic viscera into loops of varying lengths over the spermatic
and opposes sudden increases in intra-abdominal cord.
pressure, as in forced expiration, or the Valsalva
maneuver. Although the muscle fibers are striated, this is not
usually a voluntary muscle. Stimulation of the skin
Innervation: on the medial thigh evokes a reflex response, the
S2-S3 spinal nerves (pudendal nerve) (ventral rami) cremasteric reflex.
and nerves from sacral plexus
Found as a vestige in women.
116 COCCYGEUS
Function:
Origin: Elevation of testes toward superficial inguinal ring
Ischium (spine and pelvic surface) Thermoregulation of testes by adjusting position
Sacrospinous ligament
Innervation:
Insertion: L 1 - L 2 spinal nerves (genitofemoral nerve) (ventral
Coccyx (lateral margins) rami)
Sacrum (last or 5th segment, side)
118 TRANSVERSUS PERINEI
Description: SUPERFICIALIS
The paired muscle lies posterior and superior to
the levator ani and contiguous with it in the same Origin:
plane. The muscle occasionally is absent. It is
considered the pelvic aspect of the sacrospinous Ischial tuberosity (inner and anterior part)
ligament.
Insertion:
Function: Perineal body (a centrally placed, modiolar-like
The coccygei pull the coccyx forward and support it structure on which perineal muscles and fascia
after it has been pushed back for defecation or converge)
parturition. Tendon of perineum
With the levatores ani and piriformis, this muscle
compresses the posterior pelvic cavity and outlet Description:
in women ("the birth canal"). A narrow slip of muscle in both the male and the
female perineum, it courses almost transversely
across the perineal area in front of the anus. It is
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Part 3. Skeletal Muscles of the Human Body
joined on the perineal body by the muscle from Description:
the opposite side. The muscle is sometimes absent,
is poorly developed, or may be doubled. Surrounds the orifice of the vagina and covers the
lateral parts of the vestibular bulb. The fibers run
Function: anteriorly on each side of the vagina and send a
Bilateral action serves to fix the centrally located slip to cover the clitoral body.
perineal body Function:
Support of pelvic viscera Arrests micturition; helps to empty urethra after
bladder empties
Innervation: nerves (pudendal nerve) (ventral Constriction of vaginal orifice
S2-S4 spinal Constriction of deep dorsal vein of clitoris by anterior
rami) fibers, contributing to erection of clitoris
119 TRANSVERSUS PERINEI Innervation:
PROFUNDUS S2-S4 spinal nerves (pudendal nerve) (ventral rami)
Origin: In the male:
Ischium (ramus, medial aspect)
Insertion: Origin:
Male: Perineal body
Female: Vagina (side); perineal body Perineal body
Median raphe over bulb of penis
Description:
Small deep muscle with similar structure and func- Insertion:
tion in both male and female. The bilateral Urogenital diaphragm (inferior fascia)
muscles meet at the midline on the perineal Aponeurosis over corpus spongiosum penis
body. This muscle is in the same plane as the Body of penis anterior to ischiocavernosus
sphincter urethrae, and together they form Tendinous expansion over dorsal vessels of penis
most of the bulk of the urogenital diaphragm.
(Together they were previously called the con- Description:
strictor urethrae.) T h e two muscles work together
to "tether" the perineal body. Located in the midline of the perineum anterior
to the anus and consisting of two symmetrical
Function: parts united by a tendinous raphe. Its fibers di-
Fixation of perineal body vide like the halves of a feather. T h e posterior
Supports pelvic viscera fibers disperse on the inferior fascia of the
urogenital diaphragm; the middle fibers encircle
Innervation: the penile bulb and the corpus spongiosum and
S2-S4 spinal form a strong aponeurosis with fibers from the
rami) opposite side; and the anterior fibers spread out
over the corpora cavernosa.
nerves (pudendal nerve) (ventral Function:
Empties urethra at end of micturition (is capable of
120 BULBOSPONGIOSUS arresting urination)
Middle fibers assist in penis erection by compressing
Formerly called:
Male: B u l b o c a v e r n o u s ; accelerator urinae the bulbar erectile tissue; anterior fibers assist by
Female: Sphincter vaginae constricting the deep dorsal vein
Contracts repeatedly in ejaculation
In the female:
Innervation: nerves (pudendal nerve) (ventral
Origin: S2-S4 spinal
Perineal body rami)
Blending with sphincter ani externus and median
raphe 121 ISCHIOCAVERNOSUS
Fascia of urogenital diaphragm
In the female:
Insertion:
Corpora cavernosus clitoridis Origin:
Ischium (tuberosity [inner surface] and ramus)
Crus clitoridis (surface)
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Insertion: Function:
Aponeurosis, inserting into sides and inferior surface Constricts urethra, particularly when the bladder
of crus clitoridis contains fluid.
It is relaxed during micturition but contracts to expel
Description: remaining urine after micturition.
Covers the unattached surface of crus clitoridis.
Muscle is smaller than the male counterpart. Innervation:
Pudendal nucleus (Onuf's nucleus)
Function: S2-S4 spinal nerves (pudendal nerve) (ventral rami)
Compresses crus clitoridis, retarding venous return
and thus assisting erection In the male:
Innervation: Origin:
S2-S4 spinal nerves (pudendal) Ischiopubic ramus (superior fibers)
Transverse perineal ligament (inferior fibers)
In the male:
Insertion:
Origin: Perineal body (converges with muscles from other
Ischium (tuberosity, medial aspect dorsal to crus penis side)
and ischial rami)
Description:
Insertion: Surrounds entire length of membranous portion of
Aponeurosis into the sides and undersurface of the urethra and is enclosed in the urogenital
body of the penis diaphragm fascia
Description: Function:
The muscle is paired and covers the crus of the Compression of urethra (bilateral action)
penis. Active in ejaculation
Relaxes during micturition but contracts to expel last
Function: crus penis, maintaining erection of urine
Compression of return of blood through the
by retarding Innervation:
veins Pudendal nerve nucleus (Onuf's nucleus)
S2-S4 spinal nerves (ventral rami)
Innervation:
S2-S4 spinal nerves (pudendal nerve, perineal 1 23 SPHINCTER ANI EXTERNUS
branch) (ventral rami)
Origin:
1 22 SPHINCTER URETHRAE Skin surrounding margin of anus
Coccyx (via anococcygeal ligament)
In the female:
Insertion:
Origin: Perineal body
Pubis (inferior ramus on each side)
Transverse perineal ligament and fascia Blends with other muscles in area
Insertion: Description:
Surrounds lower urethra, neck of bladder; sends fibers Surrounds entire anal canal and is adherent to skin.
to wall of vagina Consists of three parts, all skeletal muscle:
Blends with fibers from opposite muscle posterior to 1. Subcutaneous: Around lower anal canal; fibers
urethra
course horizontally beneath the skin at the anal
Peroneal membrane (posterior edge) orifice. Some fibers join perineal body and others
join the anococcygeal ligament.
Description: 2. Superficial: Surrounds the lower part of the inter-
nal sphincter; attaches to both the perineal body
Has both superior and inferior fibers. The inferior and the coccyx (via the terminal coccygeal ligament,
fibers arise on the pubis and course across the the only bony attachment of the muscle).
pubic arch in front of the urethra to circle around 3. Deep part: T h i c k band around the upper internal
it. The superior fibers merge into the smooth sphincter with fibers blending with the pubo-
muscle of the bladder. rectalis of the levator ani and fascia.
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Part 3. Skeletal Muscles of the Human Body
Function: Description:
Keeps anal orifice closed. It is always in a state of A flat, triangular muscle lying over the posterior
tonic contraction and has no antagonist. Muscle neck, shoulder, and upper thorax. The upper
relaxes during defecation, allowing orifice to trapezius fibers course down and laterally from
open. The muscle can be voluntarily contracted the occiput; the middle fibers are horizontal;
to close the orifice more tightly as in forced and the lower fibers move upward and laterally
expiration or the Valsalva maneuver. from the vertebrae to the scapular spine. The
name of the muscle is derived from the shape
Innervation: of the muscle with its contralateral partner: a
S2-S3 spinal nerves (pudendal nerve, inferior rectal diamond-shaped quadrilateral figure, or trape-
branch) (ventral rami) zoid.
S4 spinal nerve (perineal branch)
Function:
All: Stabilizes scapula during movements of the
arm
MUSCLES OF THE UPPER EXTREMITY Upper and lower:
(Shoulder Girdle, Elbow,
Forearm, Wrist, Fingers, Thumb) Rotation of the scapula so glenoid laces up (in-
ferior angle moves laterally and forward)
Upper:
Elevation of scapula and shoulder ("shrugging")
Muscles of the Shoulder Girdle (with levator scapulae)
Acting on the Scapula
Rotation of head to opposite side (one)
124 Trapezius
125 Rhomboid major Capital extension (both)
126 Rhomboid minor
127 Levator scapulae Cervical extension (both)
128 Serratus anterior
129 Pectoralis minor Middle:
Scapular adduction (retraction) (with
rhomboids)
Lower:
Scapular adduction, depression, and upward
rotation
124 TRAPEZIUS Innervation:
Accessory (XI) nerve (upper and middle)
A paired muscle While the accessory nerve provides the major mo-
tor supply to the trapezius, there also is some
Origin: supply from the cervical plexus ( C 3 - C 4 ) , and
this may be the primary supply of the lower
Upper: fibers with contributions from the accessory
Occiput (external protuberance and medial nerve.18
of superior nuchal line)
Ligamentum nuchae 1/3
C7 vertebra (spinous process)
125 RHOMBOID MAJOR
Middle: (Rhomboideus Major)
T 1 - T 5 vertebrae (spinous processes) Origin:
Supraspinous ligaments T 2 - T 5 vertebrae (spinous processes)
Supraspinous ligaments
Lower:
T 6 - T 1 2 vertebrae (spinous processes) Insertion:
Supraspinous ligaments Scapula (medial [vertebral] border between
of spine above and inferior angle below)
root
Insertion: Description: inferolaterally
Fibers of the muscle run slightly the vertebral
Upper: between the thoracic spine and
Clavicle (posterior surface, lateral 1/3) border of the scapula.
Middle: Function:
Scapula (medial margin of acromion; spine of Scapular adduction
scapula and crest of its superior lip)
Lower:
Scapula (spine: tubercle at lateral apex and
aponeurosis at root of spine)
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Downward rotation of scapula (glenoid faces 128 SERRATUS ANTERIOR
down)
Origin:
Scapular elevation Ribs 1 to 8 (often ribs 9 and 10 also) by digitations
(superior and outer surfaces). Each digitation
Innervation: (except first) arises from a single rib. The first
C5 dorsal scapular nerve digitation arises from the 1st and 2 n d ribs. All
others arise from a single rib and fascia covering
126 RHOMBOID MINOR the intervening intercostals.
Origin: Aponeurosis of intercostal muscles
C7-T1 vertebrae (spinous processes)
Ligamentum nuchae (lower) Insertion:
Scapula (ventral surface of whole vertebral border)
Insertion: First digitation: Superior angle of scapula on anterior
Scapula (root of spine on medial [vertebral] aspect
border)
Second and third digitations: Anterior (costal) surface
Description: its of whole vertebral border
Lies just superior to rhomboid major, and
fibers run parallel with the larger muscle. Fourth to eighth digitations: Inferior angle of scapula
(costal surface)
Function: rotation (glenoid faces Description:
Scapular adduction
Scapular downward This large sheet of muscle curves posteriorly around
the thorax from its origin on the lateral side of
down) the ribs, passing under the scapula to attach to its
Scapular elevation vertebral border.
Innervation: Function:
C5 dorsal scapular nerve Scapular abduction
Upward rotation of the scapula (glenoid faces up)
Medial border of scapula drawn anteriorly close to
the thoracic wall (preventing "winging")
127 LEVATOR SCAPULAE Functional Relationships:
Origin: The serratus works with the trapezius in a force
C 1 - C 4 vertebrae (transverse processes and posterior
tubercles) couple to rotate the scapula upward (glenoid up),
Insertion: allowing the arm to be elevated fully ( 1 5 0 ° to
Scapula (vertebral border between superior angle and
root of scapular spine) 180°). Three component forces act around a
Description: center of rotation located in the center of the
Lies on the dorsolateral neck and descends deep
to the sternocleidomastoid on the floor of the scapula: (1) upward pull on the acromial end of
posterior triangle of the neck. Its vertebral
attachments vary considerably. the spine of the scapula by the upper trapezius;
Function: (2) downward pull on the base of the spine of
Elevates and adducts scapula
Scapular downward rotation (glenoid faces the scapula by the lower trapezius; (3) lateral and
down)
Lateral bending of cervical spine to same side anterior pull on the inferior angle by the inferior
(one)
Cervical rotation to same side (one) fibers of the serratus.19- 21
Cervical extension (both assist)
The reader is referred to comprehensive texts on
Innervation: kinesiology for further detail.
C 3 - C 4 spinal nerves (ventral rami)
C5 dorsal scapular nerve (to lower fibers) (ventral Innervation:
rami) C5-C7 long thoracic nerve
129 PECTORALIS MINOR
Origin:
Ribs 3 to 5 and sometimes ribs 2 to 4 (upper and
outer surfaces near the costal cartilages)
Aponeurosis of intercostal muscles
Insertion: medial border, and
Scapula (coracoid process,
superior surface)
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Description: crutch walking (elevation of trunk to arms, i.e.,
This muscle, broader at its origins, lies on the up- shoulder depression), or swinging.22
per thorax directly under the pectoralis major. Adducts raised arm against resistance (with
It forms part of the anterior wall of the axilla
(along with the pectoralis major). The fibers pectoralis major and teres major).
pass upward and laterally and converge in a flat It is very active in strong expiration, as in
tendon.
coughing and sneezing, and in deep
Function: inspiration.
Scapular protraction (abduction): scapula moves Elevation of pelvis with arms fixed
forward around the chest wall. Works here with
serratus anterior. Innervation:
Elevation of ribs in forced inspiration when scapula C 6 - C 8 thoracodorsal nerve (ventral rami)
is fixed by the levator scapulae
131 PECTORALIS MAJOR
Innervation:
C5-T1 medial and lateral pectoral nerves Origin:
Vertebrohumeral Muscles Clavicular (upper) portion:
130 Latissimus dorsi Clavicle (sternal half of anterior surface)
131 Pectoralis major Sternocostal portion:
130 LATISSIMUS DORSI Sternum (half of the anterior surface down to level
Origin: o f rib 6)
T 6 - T 1 2 vertebrae (spinous processes)
L 1 - L 5 and sacral vertebrae (spinous processes by Ribs (cartilage of all true ribs except rib 1 and
way of the thoracolumbar fascia)
Ribs 9 to 12 (interdigitates with the external ab- sometimes rib 7)
dominal oblique)
Ilium (posterior 1 /3 of iliac crest) Aponeurosis of obliquus externus abdominis
Supraspinous ligament
Insertion:
Insertion: Humerus (intertubercular sulcus, lateral border via
Humerus (intertubercular groove, floor, distal) a bilaminar tendon)
Deep fascia of arm
Description:
Description: This muscle is a large, thick, fan-shaped muscle
A broad sheet of muscle that covers the lumbar covering the anterior and superior surfaces of
and lower portion of the posterior thorax. the thorax. The pectoralis major forms part of
From this wide origin, the muscle fibers converge the anterior wall of the axilla (the anterior axillary
on the proximal humerus. The superior fibers are fold, conspicuous in abduction). The muscle is
almost horizontal, passing over the inferior angle divided into two portions that converge toward
of the scapula, whereas the lowest fibers are almost the axilla.
vertical. As the muscle ap-proaches its tendinous
insertion, the fibers from the upper and lower The clavicular fibers pass downward and laterally
portions fold on themselves so that the superior toward the humeral insertion. The sternocostal
fibers are attached inferiorly in the intertubercular fibers pass horizontally from midsternum and
groove; similarly, the sacral and lumbar fibers upward and laterally from the rib attachments.
become more superior. The lower fibers rise almost vertically toward the
axilla. Both parts unite in a common tendon of
Function: insertion to the humerus.
Extension, adduction, and internal rotation of
shoulder Function:
Hyperextension of spine (muscles on both sides), as Adduction of shoulder (glenohumeral) joint
in lifting (whole muscle, proximal attachment fixed)
The muscle is most powerful in overhead activities Internal rotation of shoulder
(such as swimming [downstroke] and climbing),
Elevation of thorax in forced inspiration (with
both upper extremities fixed)
Clavicular fibers:
Internal rotation of shoulder
Flexion of shoulder
Horizontal shoulder adduction
Sternocostal fibers:
Horizontal shoulder adduction
Extension of shoulder
Draws trunk upward and forward in climbing
Innervation:
Clavicular fibers: C 5 - C 7 lateral pectoral nerve
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Sternocostal fibers: C 6 - T 1 medial and lateral Description:
pectoral nerves This large multipennate, triangular muscle covers
the shoulder anteriorly, posteriorly, and laterally.
Scapulohumeral Muscles From a wide origin on the scapula and clavicle,
all fibers converge on the humeral insertion,
There are six shoulder muscles, which extend from where it gives off an expansion to the deep
the scapula to the humerus. Also included here are fascia of the arm. The anterior fibers descend
the subclavius and the coracobrachialis. obliquely backward and laterally; the middle
fibers descend vertically; the posterior fibers
132 Subclavius descend obliquely forward and laterally.
133 Deltoid Function:
Abduction of shoulder (glenohumeral joint):
135 Supraspinatus primarily the acromial middle fibers. The
anterior and posterior fibers in this motion
136 Infraspinatus stabilize the limb in its cantilever position.
Flexion and internal rotation of shoulder (anterior
134 Subscapularis fibers)
Extension and external rotation: posterior fibers
138 Teres major The deltoid tends to displace the humeral head
upward.
137 Teres minor Shoulder horizontal abduction (posterior fibers)
Shoulder horizontal adduction (anterior fibers)
139 Coracobrachialis
Innervation:
All act on the shoulder (glenohumeral) joint. The C 5 - C 6 axillary nerve (ventral rami)
largest of the muscles (deltoid) also attaches to the
clavicle and overlies the remaining muscles. 134 SUBSCAPULARIS
132 SUBCLAVIUS Origin:
Scapula (subscapular fossa and groove along
Origin: axillary margin)
Aponeurosis separating this muscle from the teres
Rib 1 and its cartilage (at their junction) major and triceps brachii (long head)
Tendinous laminae
Insertion:
Insertion:
Clavicle (inferior surface, groove in middle 1/3) Humerus (lesser tubercle)
Capsule of glenohumeral joint (anterior)
Description:
A small elongated muscle lying under the clavicle Description:
between it and the 1st rib. The fibers run This is one of the rotator cuff muscles. It is a
upward and laterally, following the contour of large triangular muscle that fills the subscapular
the clavicle. fossa of the scapula. The tendon of insertion is
separated from the scapular neck by a large
Function: bursa, which is really a protrusion of the
Shoulder depression (assist) synovial lining of the joint. Variations are rare.
Depresses and moves clavicle forward, thus
stabilizing it during shoulder motion Function:
Internal rotation of shoulder joint
Innervation: Stabilization of glenohumeral joint by humeral
C 5 - C 6 (nerve to subclavius off brachial plexus) depression (keeps humeral head in glenoid
(ventral rami) fossa)
133 DELTOID Innervation:
C 5 - C 6 subscapular nerves (upper and lower)
Origin:
Anterior fibers: Clavicle (shaft: anterior border and 135 SUPRASPINATUS
superior surface of lateral 1/3)
Middle fibers: Scapula (acromion, lateral margin, Origin:
and superior surface) Scapula (supraspinous fossa, medial 2/3)
Posterior fibers: Scapula (spine on lower lip of Supraspinatus fascia
posterior border)
Insertion:
Humerus (deltoid tuberosity on lateral midshaft via
humeral tendon)
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Insertion: Humerus (shaft: below the lowest facet, lower
Humerus (greater tubercle, highest facet) fibers)
Articular capsule of glenohumeral joint
Capsule of glenohumeral joint (posterior)
Description: Description:
This is one of the four rotator cuff muscles.
Occupying all of the supraspinous fossa, the A somewhat cylindrical and elongated muscle, the
muscle fibers converge to form a flat tendon teres minor ascends laterally and upward from
that crosses above the glenohumeral joint (be- its origin to form a tendon that inserts on the
neath the acromion) on its way to a humeral greater tubercle of the humerus. It lies inferior
insertion. This tendon is the most commonly to the infraspinatus, and its fibers lie in parallel
ruptured element of the rotator cuff mechanism with that muscle. It is one of the rotator cuff
around the joint. muscles.
Function: Function: fossa, thus
Maintains humeral head in Maintains humeral head in glenoid
other rotator cuff muscles) glenoid fossa (with stabilizing the shoulder joint
Abduction of shoulder External rotation of shoulder
External rotation of shoulder Adduction of shoulder (weak)
Innervation: Innervation:
C5-C6 suprascapular nerve C 5 - C 6 axillary nerve
136 INFRASPINATUS 138 TERES MAJOR
Origin: Origin:
Scapula (fills most of infraspinous fossa, rises from Scapula (dorsal surface near the inferior scapular angle
medial 2 / 3 ) on its lateral margin)
Infraspinous fascia Fibrous septa between this muscle and the teres minor
and infraspinatus
Insertion: Insertion:
Humerus (greater tubercle, middle facet) Humerus (intertubercular sulcus, medial lip)
Description: Description:
Occupies most of the infraspinous fossa. The muscle The teres major is a flattened but thick muscle
fibers converge to form the tendon of insertion, that ascends laterally and upward to the
which glides over the lateral border of die scapular humerus. Its tendon lies behind that of the
spine and then passes across the posterior aspect latissimus dorsi, and they generally unite for a
of the articular capsule to insert on the humerus. short distance.
This is the third of the rotator cuff muscles.
Function:
Function: Internal rotation of shoulder
Stabilizes shoulder joint by depressing humeral head Adduction and extension of shoulder
in glenoid fossa Extension of shoulder from a flexed position
External rotation of shoulder
Innervation: Innervation:
C 5 - C 6 suprascapular nerve C 5 - C 6 subscapular nerve (lower)
137 TERES MINOR 139 CORACOBRACHIALIS
Origin: Origin:
Scapula (proximal 2 / 3 of flat surface on dorsal as- Scapula, coracoid process (apex)
pect of axillary border) Intermuscular septum
Aponeurotic laminae (two such), one of which
separates it from the teres major, the other from Insertion:
the infraspinatus Humerus (midway along medial border of shaft)
Insertion: tubercle, most inferior facet, Description:
Humerus (greater
upper fibers) T h e smallest of the muscles of the arm, it lies
along the upper medial portion of the arm, ap-
pearing as a small rounded ridge. The muscle
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Part 3. Skeletal Muscles of the Human Body
fibers lie along the axis of the humerus. T h e Function:
origin on the coracoid process is in common
with the tendon of the biceps brachii (short Both heads:
head). Flexion of elbow
Supination of forearm (powerful)
Function:
Flexion of arm Long head:
Adduction of shoulder
Stabilizes and depresses humeral head in glenoid
Innervation: fossa during deltoid activity
C5-C7 musculocutaneous nerve
Innervation:
Muscles Acting on the Elbow C5-C6 musculocutaneous nerve
140 Biceps brachii 141 BRACHIALIS
141 Brachialis Origin:
Humerus (shaft: distal 1/2 of anterior surface)
142 Triceps brachii Intermuscular septa (medial 1/2)
143 Brachioradialis Insertion:
Ulna (ulnar tuberosity and rough surface of coronoid
144 Anconeus process, anterior aspect)
Anterior ligament of elbow joint
140 BICEPS BRACHII Bicipital aponeurosis (occasionally)
Origin: Description:
Short head: Positioned over the distal half of the front of the
Scapula (apex of coracoid process) humerus and the anterior aspect of the elbow joint.
Long head: It may be divided into several parts or may be
Capsule of glenohumeral joint and glenoid fused with nearby muscles.
labrum The C7 innervation by the radial nerve is to the
Scapula (supraglenoid tubercle at apex of glenoid
cavity) lateral part of the muscle and is not large.
Insertion: Function:
Radius (radial tuberosity on posterior rough Flexion of elbow, forearm supinated or pronated.
surface)
Broad bicipital aponeurosis fusing with deep fascia Innervation:
over forearm flexors C5-C6 musculocutaneous nerve
C7 radial n e r v e 2 3
Description:
Long muscle on the anterior surface of the arm 142 TRICEPS BRACHII
consisting of two heads. The tendon of origin
of the short head is thick and flat; the tendon Has three heads
of the long head is long and narrow, curving
up, over, and down the humeral head before Origin:
giving way to the muscle belly. The muscle Long head:
fibers of both heads lie fairly parallel to the axis Scapula (infraglenoid tuberosity)
of the humerus. The heads can be readily sepa- Blends above with capsule of glenohumeral joint
rated except for the distal portion near the elbow Lateral head:
joint, where they join before ending in a flat Humerus (shaft: oblique ridge on posterior surface)
tendon. Lateral intermuscular septum
The distal tendon spirals so that its anterior surface Medial head:
becomes lateral at the point of insertion.
Both the short head and the coracobrachialis arise Humerus (shaft: entire posterior surface distal to
from the coracoid apex. The muscle flexes the radial groove down almost to trochlea)
elbow most forcefully when the forearm is in
supination. It is attached, via the bicipital Medial and lateral intermuscular septa
aponeurosis, to the posterior border of the ulna, Humerus (medial border)
the distal end of which is drawn medially in
supination. Insertion: posterior
Three heads join in a common tendon.
Ulna (olecranon process, proximal
surface)
Antebrachial fascia
Capsule of elbow joint
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Description: Insertion:
Located along the entire dorsal aspect of the arm Ulna (olecranon, lateral aspect, and posterior surface
in the extensor compartment. It is a large muscle of upper 1/4 of shaft)
arising in three heads: long, lateral, and medial.
All heads join in a common tendon of insertion, Description:
which begins at the midpoint of the muscle. A A small triangular muscle on the dorsum of the
fourth head is not uncommon. elbow whose fibers descend medially a short
distance to their ulnar insertion. Considered a
Function: continuation of the triceps and often blended
Extension of elbow with it.
Long and lateral heads: Especially active in resisted
extension, otherwise minimally active24 Function:
Long head: Extension and adduction of shoulder Elbow extension (assist)
(assist)
Innervation:
Medial head: Active in all forms of extension C 6 - C 8 radial nerve
Innervation: Muscles Acting on the Forearm
C 6 - C 8 radial nerve (ventral rami)
145 Supinator
143 BRACHIORADIAUS
140 Biceps brachii (see Muscles Acting on the
Origin: (lateral supracondylar ridge, proximal Elbow)
Humerus
2/3) 146 Pronator teres
Lateral intermuscular septum (anterior) 147 Pronator quadratus
Insertion: 145 SUPINATOR
Radius (lateral side of shaft just proximal to styloid Origin:
process) Humerus (lateral epicondyle)
Radial collateral ligament of elbow joint
Description: Annular ligament of radioulnar joint
The most superficial muscle on the radial side of Ulna (dorsal surface of shaft, supinator crest)
the forearm, it forms the lateral side of the Aponeurosis of supinator
cubital fossa. It has a rather thin belly that de-
scends to the midforearm, where its long flat Insertion:
tendon begins and continues to the distal radius. Radius (tuberosity and oblique line; shaft: lateral
The brachioradialis often is fused proximally with surface of proximal 1/3)
the brachialis. Its tendon may be divided and the
muscle may be absent (rarely). Description:
Broad muscle whose fibers form two planes that curve
This is a flexor muscle despite its innervation by an around the upper radius. The two planes arise
"extensor" nerve. together from the epicondyle: the superficial plane
from the tendon and the deep plane from the
Function: muscle fibers. This muscle is subject to
considerable variation.
Flexion of elbow
Note: This muscle evolved with the extensor muscles Function:
Supination of forearm
and is innervated by the radial nerve, but its action
is that of a forearm flexor. The muscle is less active Innervation:
when the forearm is fully supinated because it C 6 - C 7 radial nerve (posterior interosseous branch)
crosses the joint laterally rather than anteriorly. It
works most efficiently when the forearm is in some 146 PRONATOR TERES
pronation.
Has two heads
Innervation:
C 5 - C 6 radial nerve (C7 innervation sometimes Origin:
cited) Humeral head (superficial and larger h e a d ) :
Shaft proximal to medial epicondyle
144 ANCONEUS
Origin:
Humerus (lateral epicondyle, posterior surface)
Capsule of elbow joint
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Common tendon of origin of forearm flexor 150 Extensor carpi ulnaris
muscles 151 Flexor carpi radialis
152 Palmaris longus
Intermuscular septum 153 Flexor carpi ulnaris
Antebrachial fascia
Ulnar head (deep head): 148 EXTENSOR CARPI
RADIALIS LONGUS
Coronoid process, medial side
Joins tendon of humeral head
Insertion: Origin:
Radius (shaft: lateral surface of middle) Humerus (distal 1/3 of lateral
ridge)
Description: supracondylar
Lateral intermuscular septum
The humeral head is much larger; the thin ulnar head Common extensor tendon
joins its companion at an acute angle, and together
they pass obliquely across the forearm to end in Insertion:
a flat tendon of insertion near the radius. T h e Second metacarpal (dorsal surface of base on radial
lateral border of the ulnar head is the medial limit side). Occasionally slips to first and third
of the cubital fossa, which lies just anterior to the metacarpals.
elbow joint. The pronator teres is less active than
the pronator quadratus.25 Description:
Descends lateral to brachioradialis. Muscle fibers end
Function: at midforearm in a flat tendon, which descends
Pronation of forearm along the lateral radius.
Elbow flexion (accessory)
Innervation: Function:
C6-C7 median nerve Extension and radial deviation of wrist
Synergist for finger flexion by stabilization of wrist
147 PRONATOR QUADRATUS Elbow flexion (accessory)
Origin: Innervation:
Ulna (shaft: oblique ridge, anterior and medial C 6 - C 7 radial nerve (lateral muscular branch)
surfaces of distal 1/4)
Aponeurosis over middle 1/3 of the muscle
Insertion: 149 EXTENSOR CARPI
Radius (shaft: anterior surface of distal 1/4; deeper RADIALIS BREVIS
fibers to a narrow triangular area above ulnar
notch) Origin:
Humerus (lateral epicondyle via common extensor
Description: tendon)
Radial collateral ligament of elbow joint
This small, flat quadrilateral muscle passes across Aponeurotic sheath and intermuscular septa
the anterior aspect of the distal ulna to the distal
radius. Its fibers are quite horizontal. The pronator Insertion:
quadratus is the main pronator of the forearm, 3rd metacarpal (dorsal surface of base on radial side
being joined by the pronator teres only in rapid distal to styloid process)
or strong motions.25 Slips sent to 2nd metacarpal base
Function: Description:
Pronation of forearm This short, thick muscle lies partially under the
extensor carpi radialis longus in the upper fore-
Innervation: nerve (anterior interosseous arm. Its muscle fibers end well above the wrist
C7-C8 median in a flattened tendon, which descends alongside
branch) the extensor carpi radialis longus tendon to the
wrist.
Muscles Acting at the Wrist
Function:
148 Extensor carpi radialis longus Extension of wrist
149 Extensor carpi radialis brevis Radial deviation of wrist (weak)
Finger flexion synergist (by stabilizing the wrist)
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Innervation: nerve (posterior interosseous
C 7 - C 8 radial
branch)
150 EXTENSOR CARPI ULNARIS
Origin:
Humerus (lateral epicondyle via c o m m o n extensor
tendon)
Ulna (posterior border by an aponeurosis common
to flexor carpi ulnaris and flexor digitorum
profundus)
Overlying fascia
Insertion:
5th metacarpal (tubercle on ulnar side of base)
Description: FIGURE 9-5 Fingers and digits of the hand,
Muscle fibers descend on the dorsal ulnar side of
the forearm and join a tendon located in the
distal 1/3 of the forearm that is the most me-
dial tendon on the dorsum of the hand. This
tendon can be palpated lateral to the groove
found just over the ulna's posterior border.
Function:
Extension of wrist
Ulnar deviation (adduction) of wrist
Innervation:
C 7 - C 8 radial nerve (posterior interosseous 152 PALMARIS LONGUS
branch)
151 FLEXOR CARPI RADIALIS Origin: flexor
Humerus (medial epicondyle via c o m m o n
Origin: tendon)
Humerus (medial epicondyle by common flexor Intermuscular septa and deep fascia
tendon)
Intermuscular septa Insertion:
Antebrachial fascia Flexor retinaculum
Palmar aponeurosis
Insertion:
2nd and 3rd metacarpals (base, palmar surface) Slip sent frequently to the short thumb muscles
Description: Description:
A slender aponeurotic muscle at its origin, it descends A slim fusiform muscle, it ends in a long tendon
in the forearm between the pronator teres and the midway in the forearm. Muscle is quite variable
palmaris longus. It increases in size as it descends and frequendy is absent.
to end in a tendon about halfway down the
forearm. Function:
Tension of palmar fascia (anchor for palmar fascia
Function: and skin)
Flexion of wrist Flexion of wrist (weak or questionable)
Radial deviation (abduction) of wrist Flexion of elbow (weak or questionable)
Extends fingers (tenodesis action) Abduction of thumb
Flexion of elbow (weak assist)
Pronation of forearm (weak assist) Innervation:
C7-C8 median nerve
Innervation: 153 FLEXOR CARPI ULNARIS
C6-C7 median nerve
Has two heads
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Muscles Acting on the Fingers
(Figures 9-5 and 9-6)
154 Extensor digitorum
155 Extensor indicis
156 Flexor digitorum superficialis
157 Flexor digitorum profundus
154 EXTENSOR DIGITORUM
Origin:
Humerus (lateral epicondyle via common extensor
tendon)
Intermuscular septa
Antebrachial fascia
FIGURE 9-6 The bones and joints of the hand, Insertion:
Origin: Digits 2 to 5: Divides distally into four tendons that
Humeral head: insert into the digital expansion over the proximal
Humerus (medial epicondyle via c o m m o n flexor and middle phalanges
tendon)
Ulnar head: Intermediate slips: To middle phalanges
Ulna (olecranon, medial border and shaft: upper Lateral slips: Distal phalanges (dorsum of base of
2 / 3 of posterior border via an aponeurosis)
Intermuscular septum digits 2 to 5)
Insertion: Description:
Pisiform bone The extensor digitorum is the only extensor of
Hamate bone the metacarpophalangeal (MP) joints. The mus-
5th metacarpal (occasionally 4th) cle divides above the wrist into four distinct
Flexor retinaculum tendons that traverse (with the extensor indicis)
a tunnel under the extensor retinaculum in a
Description: c o m m o n sheath. Over the dorsum of the hand,
This is the most ulnar-lying of the flexors in the the four tendons diverge, one to each finger. The
forearm. The humeral head is small in contrast tendon to the index finger is accompanied by the
to the extensive origin of the ulnar head. The extensor indicis tendon.
two heads are connected by a tendinous arch
under which the ulnar nerve descends. The The digital attachments are achieved by a fibrous
muscle fibers end in a tendon that forms along expansion dorsal to the proximal phalanges. All
the anterolateral border of the muscle's distal of the digital extensors, as well as the lumbri-
half. cales and interossei, are integral to this mecha-
nism.
Function:
Flexion of wrist Function:
Ulnar deviation (adduction) of wrist Extension of MP and proximal (PIP) and distal
Flexion of elbow (assist) interphalangeal (DIP) joints, digits 2 to 5
Extensor digitorum can extend any and all joints over
Innervation:
C7-T1 ulnar nerve which it passes via the dorsal expansion.
Independent action of the extensor digitorum:
Hyperextends MP joint (proximal phalanges) by
displacing dorsal expansion proximally
Extends IP joints (middle and distal phalanges)
when MP joints are slightly flexed by
intrinsics
Wrist extension (accessory)
Abduction of ring, index, and little fingers with
extension but no such action on the middle
finger
Innervation: nerve (posterior interosseous
C 7 - C 8 radial
branch)
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155 EXTENSOR INDICIS 2 and 5. This can be remembered by touching
the tips of the little and index fingers (deep)
Origin: below origin of together underneath the ring and middle fingers
Ulna (posterior surface of shaft (superficial).
extensor pollicis longus) The four tendons sweep under the flexor retinac-
Interosseous membrane ulum arranged in pairs (for the long and
ring fingers, and for the index and little fin-
Insertion: gers). The tendons diverge again in the palm, and
Index finger (2nd digit) (extensor hood) at the base of the proximal phalanges each
divides into two slips to permit passage of the
Description: flexor digitorum profundus to each finger. The
slips reunite and then divide again for a final
Arises just below the extensor pollicis longus and time to insert on both sides of each middle-
travels adjacent with it down to the level of the phalanx.
wrist. After passing under the extensor retinacu-
lum near the head of the 2nd metacarpal, it The radial head may be absent.
joins with the index tendon of the extensor
digitorum on its ulnar side and then inserts Function:
into the extensor hood of the 2nd digit. Flexion of PIP joints of digits 2 to 5
Flexion of MP joints of digits 2 to 5 (assist)
Function: Flexion of wrist (accessory, especially in forceful
Extension of MP joint of index finger grasp)
Extension of IP joints (with intrinsics)
Adduction of index finger (accessory) Innervation:
Wrist extension (accessory) C8-T1 median nerve
Innervation: nerve (posterior interosseous 157 FLEXOR DIGITORUM
C 7 - C 8 radial PROFUNDUS
branch)
Origin:
156 FLEXOR DIGITORUM Ulna (shaft: upper 3/4 of anterior and medial
SUPERFICIALIS surfaces; also coronoid process, medial side via an
aponeurosis)
Has t w o heads Interosseous membrane (ulnar half)
Origin: Insertion:
Ends in four tendons:
Humeral-ulnar head: Digits 2 to 5 (distal phalanges, palmar surface and
base). Index finger tendon is distinct in its
Humerus (medial epicondyle via the common course.
flexor tendon) Description:
Lying deep to the superficial flexors, the profun-
Ulnar collateral ligament of elbow joint dus is located on the ulnar side of the forearm.
The muscle fibers end in four tendons below
Ulna (coronoid process, medial side) the midforearm; the tendons pass into the hand
under the transverse carpal ligament. The ten-
Intermuscular septa don for the index finger remains distinct, but
the tendons for the other fingers are inter-
Radial head: twined and connected to tendinous slips down
into the palm.
Radius (oblique line on anterior surface ofshaft) After passing through the tendons of the flexor
digitorum superficialis, they move to their
Insertion: insertions on each distal phalanx. The four
From four tendons arranged in two pairs: lumbrical muscles arise from the profundus
Superficial pair: L o n g and ring fingers (sides of tendons in the palm.
middle phalanges) T h e profundus, like the superficialis, can flex any or
Deep pair: Index and little fingers (sides of middle all joints over which it passes, but it is the
only muscle that can flex the DIP joints.
phalanges)
Description:
Lies deep to the other forearm flexors but is the
largest superficial flexor. The muscle separates into
two planes of fibers, superficial and deep. The
superficial plane (joined by radial head) divides
into two tendons for digits 3 and 5. The deep
plane fibers divide and join the tendons to digits
Chapter 9 / Ready Reference Anatomy 4 0 7
Part 3. Skeletal Muscles of the Human Body
Function: Innervation: nerve (posterior interosseous
Flexion of DIP joints of digits 2 to 5 C 7 - C 8 radial
Flexion of MP and PIP joints of digits 2 to 5 branch)
(assist)
159 ABDUCTOR DIGITI MINIMI
Flexion of wrist (accessory)
Origin:
Innervation: Pisiform bone (often passes a slip to 5th metacarpal)
C8-T1 median nerve (anterior interosseous nerve) Tendon of flexor carpi ulnaris
for digits 2 and 3 Pisohamate ligament
C 8 - T 1 ulnar nerve for digits 4 and 5
Insertion:
Muscles Acting on the Little Finger 5th digit (proximal phalanx, base on ulnar side)
(and Hypothenar Muscles) Into dorsal digital expansion of extensor digiti
minimi
158 Extensor digiti minimi
Description:
159 Abductor digiti minimi Located on the ulnar border of the palm
160 Flexor digiti minimi brevis Function:
Abduction of 5th digit away from ring finger
161 Opponens digiti minimi Flexion of proximal phalanx of 5th digit at the MP
joint
162 Palmaris brevis
Opposition of 5th digit (assist)
158 EXTENSOR DIGITI MINIMI
Innervation:
Origin: C 8 - T 1 ulnar nerve (deep branch)
Common extensor tendon
Intermuscular septa 160 FLEXOR DIGITI MINIMI BREVIS
Antebrachial fascia
Origin: along with
Insertion: Hamate bone (hamulus or "hook")
Digit 5 via extensor hood on the radial side, as a Flexor retinaculum (palmar surface
separate long tendon to the little finger. From its abductor digiti minimi)
origin in the forearm, the long tendon passes under
the extensor retinaculum at the wrist. The tendon Insertion:
divides into two slips: one joining the extensor 5th digit (proximal phalanx, base on ulnar side along
digitorum to the 5th digit. All three tendons then with abductor digiti minimi)
join the extensor hood, which covers the dorsum
of the proximal phalanx. Description:
This short flexor of the little finger lies in the same
Description: plane as the abductor digiti minimi on its radial
A slim extensor muscle that lies medial to the extensor side. The muscle may be absent or fused with the
digitorum and usually is associated with that abductor.
muscle. It descends in the forearm (between the
extensor digitorum and the extensor carpi ulnaris), Function:
passes under the extensor retinaculum at the wrist Flexion of little finger at the MP joint
in its own compartment, and then divides into Opposition of 5th digit (assist)
two tendons. The lateral tendon joins directly with
the tendon of the extensor digitorum; all three Innervation:
join the extensor expansion, and all insert on the C 8 - T 1 ulnar nerve (deep branch)
middle phalanx of digit 5. The extensor digiti
minimi can extend any of the joints of digit 5 via 161 OPPONENS DIGITI MINIMI
the dorsal digital expansion.
Origin:
Function: Hamate (hamulus or "hook")
Extension of MP, IP, and DIP joints of digit 5 (little Flexor retinaculum
finger)
Wrist extension (accessory) Insertion:
Abduction of digit 5 (accessory) 5th metacarpal (entire length of ulnar margin)
4 0 8 Chapter 9 / Ready Reference Anatomy
Part 3. Skeletal Muscles of the Human Body
Description: FIGURE 9-7 The lumbricales, palmar view,
A triangular muscle lying deep to the abductor and
the flexor. It commonly is blended with its corresponding digit and attaches to the dorsal
neighbors. digital expansion:
First lumbrical: To index finger (digit 2)
Function: Second lumbrical: To long (middle) finger (digit 3)
Opposition of little finger to thumb (abduction, Third lumbrical: To ring finger (digit 4)
flexion, and lateral rotation, deepening the palmar Fourth lumbrical: To little finger (digit 5)
hollow)
Description:
Innervation: These four small muscles arise from the tendon of
C8-T1 ulnar nerve (deep branch) the flexor digitorum profundus over the
metacarpals. They may be unipennate or
162 PALMARIS BREVIS bipennate. They extend to the middle phalanges
of digits 2 to 5 (fingers 1 to 4 ) , where they join
Origin: the dorsal extensor hood on the radial side of each
digit (see Figure 9 - 7 ) . Essentially, they link the
Flexor retinaculum and palmar aponeurosis flexor to the extension tendon systems in the hand.
The exact attachments are quite variable. This gives
Insertion: rise to complexity of movement and differences in
Skin on ulnar border of palm (hypothenar description.26
eminence)
Function:
Description: Flexion of MP joints (proximal phalanges) of digits
A thin superficial muscle whose fibers run directly 2 to 5 and simultaneous extension of the PIP and
laterally across the hypothenar eminence DIP joints
Opposition of digit 5 (fourth lumbrical)
Function:
Draws the skin of the ulnar side of the hand toward Innervation:
the palm. This deepens the hollow of the hand First and second lumbricales: C8-T1 median nerve
and seems to increase the height Third and fourth lumbricales: C8-T1 ulnar nerve
of the hypothenar eminence, possibly assisting Note: The third lumbrical may receive innervation
in grasp. from both the ulnar and the median nerves or all
from the median nerve.
Innervation:
C 8 - T 1 ulnar nerve (superficial branch)
Intrinsic Muscles of the Hand
163 Lumbricales
164 Interossei, dorsal
165 Interossei, palmar
163 LUMBRICALES (Figure 9-7)
Origin:
Flexor digitorum profundus tendons:
1st lumbrical: Index finger (digit 2 ) ; arises by single
head from the radial side, palmar surface
2nd lumbrical: L o n g (middle) finger (digit 3 ) , radial
side, palmar surface
3rd lumbrical: L o n g and ring fingers (digits 3 and
4) by double heads from adjacent sides of tendons
of flexor digitorum profundus
4tb lumbrical: Ring and little fingers (digits 4 and
5 ) , adjacent sides of tendon
Insertion:
Extensor digitorum expansion
Each muscle extends distally to the radial side of its
Chapter 9 / Ready Reference Anatomy 4 0 9
Part 3. Skeletal Muscles of the Human Body
Flexion of fingers at MP joints (assist)
Extension of fingers at IP joints (assist)
Thumb adduction (assist)
Innervation:
C8-T1 ulnar nerve (deep branch)
165 PALMAR (VOLAR) INTEROSSEI
(Figure 9-9)
There are three palmar interossei muscles (a fourth
muscle is described).
Origin:
Metacarpal bones 2, 4, and 5. These muscles lie on
the palmar surface of the metacarpals rather than
between them. There is no palmar interosseous on
the long finger.
1st palmar: 2 n d metacarpal (ulnar side)
2nd palmar: 4 t h metacarpal (radial side)
3rd palmar: 5th metacarpal (radial side)
FIGURE 9-8 The dorsal interossei. Insertion:
All: Dorsal expansion
164 DORSAL INTEROSSEI (Figure 9-8)
Proximal phalanges (ulnar side)
There are four bipennate muscles. 1st palmar: Index finger (radial side)
2nd palmar: Ring finger (radial side)
3rd palmar: Little finger
Origin:
Each muscle arises by two heads from adjacent sides of
the metacarpals between which each lies.
1st dorsal (also called abductor indicis): Between
thumb and index fingers
2nd dorsal: Between index and long fingers
3rd dorsal: Between long and ring fingers
4tb dorsal: Between ring and little fingers
Insertion:
All: Dorsal extensor expansion
Proximal phalanges (bases)
1st dorsal: Index finger (radial side)
2nd dorsal: L o n g finger (radial side)
3rd dorsal: L o n g finger (ulnar side)
4th dorsal: Ring finger (ulnar side)
Description:
This group comprises four bipennate muscles (see
Figure 9 - 8 ) . In general, they originate via two
heads from the adjacent metacarpal but more so
from the metacarpal of the digit where they will
insert distally. They insert into the bases of the
proximal phalanges and dorsal expansions.
Function: FIGURE 9-9 The palmar (volar) interossei.
Abduction of fingers away from an axis drawn
through the center of the long (middle) finger
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Part 3. Skeletal Muscles of the Human Body
Description: along with the tendon of the extensor pollicis
The palmar interossei are smaller than their dorsal brevis. Its tendon is commonly split; one slip
counterparts. They are found on the palmar attaches to the radial side of the 1st metacarpal
surface of the hand at the metacarpal bones. and the other to the trapezium.27
There are three very distinct volar interossei
(see Figure 9 - 9 ) , and some authors describe a Function:
4th interosseus, to which they give the number Abduction and extension of thumb at
1 for its attachment on the thumb. When the carpometacarpal ( C M C ) joint
4th interosseus is found as a discrete muscle, the Extension of thumb at C M C joint (in concert with
other palmar interossei become numbers 2 , 3 , and thumb extensors)
4, respectively. When the thumb interosseus exists, Radial deviation of wrist (assist)
it is on the ulnar side of the metacarpal and Wrist flexion (weak)
proximal phalanx. Some authors (including us)
consider the interosseus of the thumb part of the Innervation: nerve (posterior interosseous
adductor pollicis. C 7 - C 8 radial
The middle finger has no interosseous muscle. branch)
Function: 167 EXTENSOR POLLICIS LONGUS
Adduction of fingers (index, ring, and little) to-
ward an axis drawn through the center of the Origin:
long finger Ulna (posterolateral surface of middle shaft)
Flexion of MP joints (assist) Interosseous membrane
Extension of IP joints (assist)
Opposition of digit 5 (3rd interroseus) Insertion:
Thumb (base of distal phalanx, dorsal side)
Innervation:
C8-T1 ulnar nerve (deep branch) Description:
Muscles Acting on the Thumb The muscle rises distal to the abductor pollicis
longus and courses down and lateral into a
166 Abductor pollicis longus tendon over the distal radius, which lies in a
narrow oblique groove on the dorsal radius. It
167 Extensor pollicis longus descends obliquely over the tendons of the carpal
extensors. It separates from the extensor
168 Extensor pollicis brevis pollicis brevis and can be seen during thumb
extension as the ulnar margin of a triangular
169 Flexor pollicis longus depression called the anatomical snuff box.
This is a larger muscle than the extensor pollicis
171 Abductor pollicis brevis brevis.
172 Opponens pollicis Function:
Extension of the t h u m b at all joints:
170 Flexor pollicis brevis Distal phalanx (alone)
MP and C M C joints (along with extensor pollicis
173 Adductor pollicis brevis and abductor pollicis longus)
Radial deviation of wrist (accessory)
166 ABDUCTOR POLLICIS LONGUS
Innervation: nerve (posterior interosseous
Origin: C 7 - C 8 radial
Ulna (posterior surface of shaft) branch)
Radius (middle 1/3 of posterior surface of shaft)
Interosseous membrane 168 EXTENSOR POLLICIS BREVIS
Insertion: Origin:
1st metacarpal bone (radial side of base) Radius (posterior surface of shaft)
Trapezium bone Interosseous membrane
Description: Insertion:
Lies immediately below the supinator and some- Thumb (proximal phalanx base on dorsal
times is fused with that muscle. Traverses surface)
obliquely down and lateral to end in a tendon at
the wrist. The tendon passes through a Attachment to distal phalanx via tendon of extensor
groove on the lateral side of the distal radius pollicis longus is c o m m o n . 2 7
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Part 3. Skeletal Muscles of the Human Body
Description: Insertion:
Arises distal and lies medial to the abductor pollicis T h u m b (both heads: proximal phalanx, base on radial
longus and descends with it so that the tendons side)
of the two muscles pass through the same groove
on the lateral side of the distal radius. During its Description:
descent, it wraps itself around a bony fulcrum The superficial head runs more laterally and
(Lister's tubercle), which alters the line of pull accompanies the flexor pollicis longus. Its tendon
from forearm to thumb. of insertion contains the radial sesamoid bone at
a point where it unites with the tendon of the
The muscle often is connected with the abductor or deep head. The deep head is sometimes absent.
may be absent. Its tendon forms the radial margin Of the thenar muscles, only the abductor pollicis
of the "snuff box." brevis consistently joins the dorsal extensor
expansion of the thumb.
Function: CMC joint of
Extension of MP joint of thumb Function:
Extension and abduction of 1st Flexion of the MP and C M C joints of the thumb
thumb Opposition of thumb (assist)
Radial deviation of wrist (accessory) Innervation:
Superficial head: C 8 - T 1 median nerve (lateral
Innervation: nerve (posterior interosseous branch)
Deep head: C 8 - T 1 ulnar nerve (deep branch)
C 7 - C 8 radial POLLICIS LONGUS
branch) 171 ABDUCTOR POLLICIS BREVIS
169 FLEXOR Origin:
Flexor retinaculum
Origin: of Scaphoid bone (tubercle)
Radius (grooved anterior surface of middle Trapezium bone (tubercle)
shaft) Tendon of abductor pollicis longus
Interosseous membrane Insertion:
Ulna (coronoid process), variable T h u m b (proximal phalanx, radial side of base)
Humerus (medial epicondyle), variable28 Dorsal extensor expansion of thumb
Insertion: Description:
Thumb (base of distal phalanx, palmar surface) The most superficial muscle on the radial side of the
thenar eminence
Description:
Function:
Descends on the radial side of the forearm in the Abduction at C M C and MP joints (in a plane 90°
same plane as, but lateral to, the flexor digito- from the palm)
rum profundus Opposition of thumb (assist)
Extension of IP joint (assist)
Function: joints of thumb
Flexion of IP joint of thumb Innervation:
Flexion of the MP and C M C C8-T1 median nerve
(accessory)
Flexion of wrist (accessory) 1 72 OPPONENS POLLICIS
Innervation: nerve (anterior interosseous Origin:
C7-C8 median Trapezium bone (tubercle)
branch) Flexor retinaculum
1 70 FLEXOR POLLICIS BREVIS Insertion:
1st metacarpal bone (along entire length of radial
Has two heads [lateral] side of shaft)
Origin: Description:
Superficial head: A small triangular muscle lying deep to the
Flexor retinaculum (distal border) abductor
Trapezium bone (tubercle)
Deep bead:
Trapezoid bone
Capitate bone
Palmar ligaments of distal row of carpal bones
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Part 3. Skeletal Muscles of the Human Body
Function: 175 Psoas minor
Flexion of C M C joint medially across the palm
Abduction of CMC joint 176 Iliacus
Medial rotation of C M C joint
177 Pectineus
These motions occur simultaneously in the motion
called opposition, which brings the thumb into 178 Gracilis
contact with any of the other fingers on their
palmar digital aspect (pads). 179 Adductor longus
Innervation: (terminal branch) 180 Adductor brevis
C8-T1 median nerve
C 8 - T 1 Ulnar nerve 181 Adductor magnus
1 73 ADDUCTOR POLLICIS 182 Gluteus maximus
Rises from two heads 183 Gluteus medius
Origin: 184 Gluteus minimus
Oblique head: 185 Tensor fasciae latae
Capitate bone
2nd and 3rd metacarpal bones (bases) 186 Piriformis
Palmar carpal ligaments
Tendon sheath of flexor carpi radialis 187 O b t u r a t o r internus
Flexor retinaculum (small slip)
Unites with tendon of transverse head 188 O b t u r a t o r externus
Transverse head: 189 Gemellus superior
3rd metacarpal bone (distal 2 / 3 of palmar surface) 190 Gemellus inferior
Converges with oblique head and with first palmar
191 Quadratus femoris
interosseous
192 Biceps femoris
Insertion (both heads):
Thumb (base, proximal phalanx on ulnar side) 193 Semitendinosus
Extensor retinaculum (on its medial side) of the
thumb 194 Semimembranosus
Description: 195 Sartorius
The muscle lies deep on the palmar side of the hand
and has two heads that vary in their comparative 1 74 PSOAS MAJOR
sizes. Both heads arise from the 3rd metacarpal
and insert into both sides of the proximal phalanx7 Origin:
or, as more frequently cited, into the medial side L1-L5 vertebrae (transverse processes, inferior
of the proximal phalanx. The two heads are divided border)
by the radial artery and the extent of their T 1 2 - L 5 vertebral bodies and intervertebral disks
convergence also is variable. between them (by five digitations)
Tendinous arches across the lumbar vertebral
Function: bodies
Adduction of C M C joint of thumb (approximates
the thumb to the palm) Insertion:
Adduction and flexion of MP joint (assist) Femur (lesser trochanter)
Innervation: Description:
C8-T1 ulnar nerve (deep branch) A long muscle lying next to the lumbar spine, its
fibers descend downward and laterally. It decreases
MUSCLES OF THE LOWER EXTREMITY in size as it descends along the pelvic brim. It
passes anterior to the hip joint and joins in a
(Knee, Ankle, Toes, Hallux) tendon with the iliacus to insert on the lesser
Muscles of the Hip trochanter.
The iliopsoas muscle is a compound muscle con-
174 Psoas major sisting of the iliacus and the psoas major,
which join in a common tendon of insertion on
the lesser trochanter of the femur.
The roots from the lumbar plexus enter the mus-
cle directly and are contained within the mus-
cle; its branches move out and away from its
borders.
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Part 3. Skeletal Muscles of the Human Body
Function: tendon of the psoas major. The iliacus, act-
Hip flexion with origin fixed32 ing alone in contraction on a fixed femur,
Trunk flexion (sit-up) with insertion fixed results in flexion of the pelvis on the femur (an
(These two functions occur in conjunction with anterior tilt termed "symphysis down") of the
the iliacus.) pelvis. This leads to increased lumbar extension
Hip external (lateral) rotation (lordosis).
Flexion of lumbar spine (muscles on both sides)
Lateral bending of lumbar spine to same side (muscle Function:
on one side) Hip flexion
Flexes pelvis on femur
Innervation:
L 2 - L 4 (lumbar plexus) spinal nerves (ventral rami) Innervation:
LI also cited L2-L3 femoral nerve
1 75 PSOAS MINOR 177 PECTINEUS
Origin: Origin: iliopectineal eminence and
T12-L1 vertebral bodies (sides) and the intervertebral Pecten pubis (between
disk between them pubic tubercle)
Anterior fascia
Insertion:
Pecten pubis (i.e., pectineal line) Insertion:
Ilium (iliopectineal eminence and linea terminalis of Femur (shaft: on a line from lesser trochanter to
inner surface of the pelvis) linea aspera)
Iliac fascia
Description:
Description: A flat muscle forming part of the wall of the
Lying anterior to the psoas major, this is a long thin femoral triangle in the upper medial aspect of
muscle whose belly lies entirely within the the thigh. It descends posteriorly and laterally
abdomen along its posterior wall, but its long flat on the medial thigh.
tendon descends to the ilium. The muscle
frequently is absent. Function:
The pecten pubis, or pectineal line, is the distal Hip adduction
end of the iliopectineal line, which in turn is a Hip flexion (accessory)
segment of the linea terminalis. These three-
segments together form the anterior part of the Innervation:
pelvic brim. L2-L3 femoral nerve
L3 accessory obturator nerve (when present)
Function:
Flexion of trunk and lumbar spine (both; weak) 178 GRACILIS
Innervation: Origin:
L1 spinal nerve Pubis (inferior ramus near symphysis via apo-
neurosis)
176 ILIACUS Ischial ramus
Origin: Insertion: of shaft below tibial
Ilium (superior 2 / 3 of iliac fossa) Tibia (medial surface
Iliac crest (inner lip) condyle)
Anterior sacroiliac and iliolumbar ligaments Pes anserinus
Sacrum (lateral) Deep fascia of leg
Insertion: Description:
Femur (lesser trochanter via insertion on tendon
of the psoas major and shaft below lesser Lies most superficially on the medial thigh as a
trochanter) thin and broad muscle that tapers and narrows
distally. T h e fibers are directed vertically and
Description: join a tendon that curves around the medial
A broad flat muscle, it fills the iliac fossa and descends condyle of the femur and then around the medial
along the fossa, converging laterally with the condyle of the tibia. Its tendon is one of
three (along with those of the sartorius and
4 1 4 Chapter 9 / Ready Reference Anatomy
Part 3. Skeletal Muscles of the Human Body
semitendinosus) that unite to form the pes Innervation:
anserinus. L2-L3 or L4 obturator nerve (posterior division)
Function: 181 ADDUCTOR MAGNUS
Hip adduction
Knee flexion Origin: ischial tuberosity, inferior
Pubis (inferior ramus)
Internal (medial) rotation of knee (accessory) Ischium (inferior ramus;
and lateral aspect)
Innervation:
(ventral Insertion:
L2-L3 obturator nerve (anterior division) Femur (whole length of linea aspera and medial
rami) supracondylar line by an aponeurosis; adductor
tubercle on medial condyle via a rounded ten-
1 79 ADDUCTOR LONGUS don; the rounded tendon attaches to the medial
supracondylar line by a fibrous expansion)
Origin:
Pubis (anterior at the angle where the crest meets
the symphysis)
Insertion: Description:
Femur (by an aponeurosis on the middle 1/3 of The largest of the adductor group, this muscle is
the linea aspera on its medial lip) located on the medial thigh and appears as
three distinct bundles. The superior fibers from
Description: the pubic ramus are short and horizontal. The
The most anterior of the adductor muscles arises in
a narrow tendon and widens into a broad muscle • medial fibers move down and laterally. The
belly as it descends backward and laterally to insert most distal bundle descends almost vertically to
on the femur. a tendon on the distal 1/3 of the thigh.
As part of their function, the hip adductors are not Occasionally the fibers that arise from the ramus
frequently called upon for strenuous activity, but of the pubis are inserted into a line from the
they are capable of such. They play a major greater trochanter to the linea aspera and seem
synergistic role in the complexity of gait and in to form a distinct separate muscle. When this
some postural activities, but are relatively quiescent occurs, the muscle is called the adductor
in quiet standing. minimis.
Function: The innervation of the adductor magnus comes
Hip adduction from the anterior divisions of the lumbar plexus,
Hip flexion (accessory) suggesting a primitive flexor action for the
Hip rotation (depends on position of thigh)33 muscle.
Hip external (lateral) rotation (when hip is
extension; accessory) in Function:
Hip adduction
Innervation: Hip extension (inferior libers)
L2 or L3-L4 obturator nerve (anterior division) Hip flexion (superior fibers; weak)
The role of the adductor magnus in rotation of the
hip is dependent on the position of the thigh.33
180 ADDUCTOR BREVIS Innervation:
Superior and middle fibers: L 2 - L 4 obturator nerve
Origin: (posterior division)
Pubis (inferior ramus and body, external aspect) Inferior fibers: L 2 - L 4 sciatic nerve (tibial division)
Insertion: 182 GLUTEUS MAXIMUS
Femur (along a line from the lesser trochanter to the Origin:
proximal 1/3 of the medial lip of the linea aspera Ilium (posterior gluteal line and crest)
via an aponeurosis) Sacrum (dorsal surface)
Coccyx (lateral surface)
Description: Erector spinae aponeurosis
The muscle lies under the pectineus and adductor Sacrotuberous ligament
longus with its fibers coursing laterally and Aponeurosis of gluteus medius
posteriorly as it broadens and descends.
Function: Insertion:
Hip adduction Iliotibial tract of fascia lata
Hip flexion Femur (gluteal tuberosity)
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Part 3. Skeletal Muscles of the Human Body
Description: 184 GLUTEUS MINIMUS
The maximus is the largest and most superficial of
the gluteal muscles, forming the prominence of Origin:
the buttocks. The fibers descend laterally, in- Ilium (outer surface between the anterior and inferior
serting widely on the thick tendinous iliotibial gluteal lines; also from margin of the greater sciatic
tract. notch).
Function: iliotibial band, it Insertion:
Hip extension (powerful) Femur (greater trochanter, anterior border)
Hip external (lateral) rotation Expansion to capsule of hip joint
Hip abduction (upper fibers)
Hip adduction (lower fibers) Description:
The minimus is the smallest of the gluteal muscles
Through its insertion into the and lies immediately under the medius. Its fibers
stabilizes the knee. pass obliquely lateral and down, forming a
fan-shaped muscle that converges on the greater
Innervation: femoral trochanter.
L5-S2 inferior gluteal nerve
Function:
183 GLUTEUS MEDIUS Hip abduction
Hip internal (medial) rotation
Origin:
Ilium (outer surface between the iliac crest and the Innervation:
posterior gluteal line) L4-S1 superior gluteal nerve (superior branch)
Gluteal aponeurosis
185 TENSOR FASCIAE LATAE
Insertion:
Femur (greater trochanter, oblique ridge on lateral Origin:
surface) Ilium (iliac crest; anterior part of outer lip; anterior
superior iliac spine [ASIS])
Description: Fascia lata (deep surface)
The posterior fibers of the medius lie deep to the
maximus; its anterior 2 / 3 is covered by fascia Insertion:
(gluteal aponeurosis). It lies on the outer surface Iliotibial tract (both layers)
of the pelvis.
Description:
The gluteus medius helps to maintain erect posture The tensor descends between and is attached to
in walking. During single-limb stance when the the deep and superficial layers of the iliotibial
swing limb is raised from the ground, all body band.
weight is placed on the opposite (stance) limb, The smallish muscle belly is highly variable in length.
which should result in a noted sagging of the pelvis The muscle lies superficially on the border between
of the swing limb. The action of the gluteus the anterior and lateral thigh. Functions at the
medius on the stance limb prevents such a tilt or knee that have been attributed to the tensor could
sag. When the gluteus medius is weak, the trunk not be confirmed in E M G studies; indeed, there
tilts (lateral lean) to the weak side with each step was no electrical activity in the tensor during knee
in an attempt to maintain balance (this is the motions.34-36
deliberate compensation for the positive
Trendelenburg sign). It is called a gluteus medius Function:
sign or gait. Hip flexion
Hip internal (medial) rotation
The uncompensated positive Trendelenburg results Knee flexion (accessory via iliotibial band) once the
in a pelvic drop of the contralateral side. This is knee is flexed beyond 30° (no
the so-called Trendelenburg gait. confirmation)
Knee extension with external rotation (no
Function: confirmation)
Hip abduction (in all positions) Knee external (lateral) rotation (assist) (no
Hip internal rotation (anterior fibers) confirmation)
Hip external (lateral) rotation (posterior fibers)
Hip flexion (anterior fibers) and hip extension Innervation:
(posterior fibers) as accessory functions L4-S1 superior gluteal nerve (inferior branch)
Innervation:
L4-S1 superior gluteal nerve (inferior branch)
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186 PIRIFORMIS Innervation:
L5-S1 nerve to obturator internus off lumbosacral
Origin: plexus
Sacrum (via three digitations attached between the
1st and 4th anterior sacral foramina) 188 OBTURATOR EXTERNUS
Ilium (gluteal surface near posterior inferior iliac spine
[PIIS]) Origin: 2/3 of outer
Capsule of sacroiliac joint Pubic ramus
Sacrotuberous ligament (pelvic surface) Ischial ramus
Insertion: Obturator foramen (margin)
Femur (greater trochanter, superior border of medial Obturator membrane (medial
aspect)
surface)
Description:
Runs parallel to the posterior margin of the Insertion:
gluteus medius posterior to the hip joint. It Femur (trochanteric fossa)
lies against the posterior wall on the interior of
the pelvis. The broad muscle belly narrows to Description:
exit through the greater sciatic foramen and This flat, triangular muscle covers the external
converge on the greater trochanter. The inser- aspect of the anterior pelvic wall from a very
tion tendon often is partly blended with the broad origin on the medial margin of the obtu-
common tendon of the obturator internus and ator foramen. Its fibers pass posteriorly and lat-
gemelli. erally in a spiral to a tendon that passes behind
the femoral neck to insert in the trochanteric
Function: fossa.
Hip external (lateral) rotation
Abducts the Hexed hip (assist) (muscle probably too This muscle, along with the other small lateral
small to do much of this) rotators, may serve more postural functions (such
as stability) than prime movement. They maintain
Innervation: the integrity of hip joint actions.
S1-S2 spinal nerves (nerve to piriformis)
Function:
187 OBTURATOR INTERNUS Hip external (lateral) rotation
Hip adduction (assist)
Origin:
Pelvis (obturator foramen, around most of its margin; Innervation:
from pelvic brim to greater sciatic foramen above L3-L4 obturator nerve (posterior branch)
and obturator foramen below)
Ischium (ramus) 189 GEMELLUS SUPERIOR
Pubis (inferior ramus)
Obturator membrane (pelvic surface) Origin:
Obturator fascia Ischial spine (gluteal surface)
Insertion: Insertion:
Femur (greater trochanter, medial surface proximal Femur (greater trochanter, medial surface)
to the trochanteric fossa)
Tendon fuses with gemelli Description:
Description: Muscle lies in parallel with and superior to the
Muscle lies internal in the osteoligamentous pelvis tendon of the obturator internus, which it joins.
and also external behind the hip joint. The fibers This is the smaller of the two gemelli and may be
converge toward the lesser sciatic foramen and absent.
hook around the body of the ischium, which acts
as a pulley; it exits the pelvis via the lesser sciatic Function:
foramen, crosses the capsule of the hip joint, and Hip external (lateral) rotation
proceeds to the greater trochanter. Hip abduction with hip flexed (accessory)
Function: Innervation:
Hip external (lateral) rotation L5-S1 nerve to obturator internus (off lumbar plexus)
Abduction of flexed hip (assist)
190 GEMELLUS INFERIOR
Origin:
Ischium (tuberosity, superior surface)
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Insertion: Description:
This lateral hamstring muscle is a two-head muscle
Femur (greater trochanter, medial surface) on the posterolateral thigh. Its long head is a two-
joint muscle. The muscle fibers of the long head
Description: descend laterally, ending in an aponeurosis that
This small muscle parallels and joins the tendon of covers the posterior surface of the muscle. Fibers
the obturator internus on its inferior side. The from the short head also converge into the same
two gemelli may be considered adjunct to aponeurosis, which narrows into the lateral
the obturator internus. hamstring tendon of insertion. At the insertion
the tendon divides into two slips to embrace the
Function: fibular collateral ligament. The short head is
Hip external (lateral) rotation sometimes absent.
Hip abduction with hip flexed (weak assist)
The different nerve supply, tibial division for the long
Innervation: head and common peroneal division for the short
L5-S1 nerve to quadratus femoris (off lumbar head, reflects both flexor and extensor muscle
plexus) derivations.
191 QUADRATUS FEMORIS The biceps femoris as a posterior femoral muscle
flexes the knee and extends the hip (from a stooped
Origin: posture) against gravity. When the hip is extended,
this muscle is an external rotator of the hip. When
Ischium (tuberosity, upper external border) the knee is flexed, the biceps is an external rotator
of the knee. When at any time the body's center
Insertion: of gravity moves forward of the transverse axis of
the hip joint, the biceps femoris contracts.
Femur (quadrate tubercle on posterior aspect)
Function:
Description: Knee flexion (only the short head is a pure knee
This flat quadrilateral muscle lies between the flexor)
gemellus inferior and the adductor magnus. Its Knee external rotation
fibers pass almost horizontally, posterior to the hip
joint and femoral neck. Hip extension and external rotation (long head)
Function: Innervation:
Hip external (lateral) rotation Long head: L 5 - S 2 sciatic nerve (tibial division)
Short head: L 5 - S 2 sciatic nerve ( c o m m o n peroneal
Innervation: division)
L5-S1 nerve to quadratus femoris (off lumbar
plexus) 193 SEMITENDINOSUS
192 BICEPS FEMORIS Origin: femoris
Ischium (tuberosity, inferior medial aspect)
Origin: Aponeurosis to share tendon with biceps
Long head:
Ischium (tuberosity, inferior and medial aspects, (long head)
in common with tendon of semitendinosus) Pes anserinus
Sacrotuberous ligament
Short head: Insertion:
Femur (linea aspera, entire length of lateral lip; Tibia (shaft on proximal medial side)
lateral supracondylar line) Deep fascia of leg
Lateral intermuscular septum
Description:
Insertion: A muscle on the posteromedial thigh known for
Aponeurosis of long head distally. T h e short head its long, round tendon, which extends from
inserts into the deep surface of this midthigh to the tibia. The semitendinosus unites
aponeurosis to form the "lateral hamstring with the tendons of the sartorius and the gracilis
tendon." to form a flattened aponeurosis called the pes
Fibula (head, lateral aspect via main portion of lateral
hamstring tendon) anserinus.
Tibia (lateral condyle via lamina from lateral
hamstring tendon)37 Function:
Fascia on lateral leg Knee flexion
Knee internal rotation
Hip extension
Hip internal rotation (accessory)
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Innervation: absent. It forms the lateral border of the femoral
L5-S2 sciatic nerve (tibial division) triangle.
194 SEMIMEMBRANOSUS Function:
Hip external rotation, abduction, and flexion
Origin: Knee flexion
Ischium (tuberosity, superior and lateral facets) Knee internal rotation
Complex proximal tendon along with fibers Assists in "tailor sitting"
from biceps femoris and semitendinosus
Innervation:
Insertion: L2-L3 femoral nerve (two branches usually)
Tibia (tubercle on medial condyle)
Oblique popliteal ligament of knee joint Muscles of the Knee
Aponeurosis over distal part of muscle to form
tendon of insertion 196-200 Quadriceps femoris the
201 Articularis genus
Description: 192 Biceps femoris (see Muscles of the Hip)
The semimembranosus is the larger of the two 193 Semitendinosus (see Muscles of the Hip)
medial hamstrings. Its name derives from its 194 S e m i m e m b r a n o s u s (see Muscles of
flat, membranous tendon of origin that partially
envelops the anterior surface of the upper por- Hip)
tion of the biceps femoris and semitendinosus. 202 Popliteus
Its fibers descend from midthigh to a distal
aponeurosis, which narrows into a short, thick 196-200 QUADRICEPS FEMORIS
tendon before inserting on the tibia. The
semitendinosus is superficial to the semimem- This muscular mass on the anterior thigh has five
branosus throughout its extent. component muscles (or heads), which together make
this the most powerful muscle group in the human
Function: body. T h e five components are the great extensors of
Knee flexion the knee.
Knee internal rotation
Hip extension 196 Rectus femoris
Hip internal rotation (accessory)
197 Vastus lateralis
Innervation:
L5-S2 sciatic nerve (tibial division) 198 Vastus intermedius
195 SARTORIUS 199 Vastus medialis longus
Origin: 200 Vastus medialis oblique
Ilium (ASIS; notch below ASIS) 196 RECTUS FEMORIS
Insertion: Origin:
Tibia (proximal medial surface of the shaft distal to Arises by two tendons, which conjoin to form an
the tibial condyle) aponeurosis from which the muscle fibers arise:
Aponeurosis
Capsule of knee joint Ilium (anterior inferior iliac spine)
Acetabulum (groove above posterior rim and superior
Description:
The longest muscle in the body, its parallel fibers margin of labrum)
form a narrow, thin muscle. It descends Capsule of hip joint
obliquely from lateral to medial to just above
the knee, where it turns abruptly downward Insertion:
and passes posterior to the medial condyle Patella (base; from an aponeurosis that gradually
of the femur. It expands into a broad aponeurosis narrows into a tendon that inserts into the center
before inserting on the medial surface of the portion of the quadriceps tendon, and then into
tibia. The sartorius is the most superficial of the ligamentum patellae to a final insertion on the
the anterior thigh muscles and occasionally is tibial tuberosity)
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Description: 199 VASTUS MEDIALIS LONGUS38,39
This most anterior of the quadriceps lies 6° me-
dial to the axis of the femur. Its superficial Origin:
fibers are bipennate, but the deep fibers are Femur (intertrochanteric line, lower half; linea aspera,
parallel. It traverses a vertical course down the medial lip, proximal portion)
thigh. It is a two-joint muscle, crossing both Tendons of adductors longus and magnus
the hip and the knee, whereas the vasti are one- Medial intermuscular septum
joint muscles crossing only the knee.
Insertion:
197 VASTUS LATERALIS Patella, via an aponeurosis into the superior medial
margin of the quadriceps tendon, and then to the
Origin: ligamentum patellae and insertion into the tibial
Femur (linea aspera, lateral lip; greater trochanter, tuberosity
anterior and inferior borders; proximal in-
tertrochanteric line; gluteal tuberosity) Description:
Lateral intermuscular septum The fibers of this muscle course upward at an angle
of 15° to 18° to the longitudinal axis of the femur.
Insertion:
Patella, into an underlying aponeurosis over the 200 VASTUS MEDIALIS OBLIQUE38,39
deep surface of the muscle, which narrows and
attaches to the lateral border of the quadriceps Origin:
tendon; to a lateral expansion, which blends Femur (linea aspera, medial lip, distal portion; medial
with the capsule of the knee and the iliotibial supracondylar line, proximal portion)
tract. Tendon of adductor magnus
The quadriceps tendon joins the ligamentum Medial intermuscular septum
patellae to insert into the tibial tuberosity.
Insertion:
Description: Patella:
The lateralis is the largest of the quadriceps group Into the medial quadriceps tendon and along the
and, as its name suggests, it forms the bulk of medial margin of the patella
the lateral thigh musculature. It arises via a Expansion aponeurosis to the capsule of the knee
broad aponeurosis lateral to the femur. Its joint
fibers run at an angle of 17° to the axis of the
femur. It descends to the thigh under the iliotibial Tibial tuberosity via ligamentum patellae
band. It is the muscle of choice for biopsy in the
lower extremity. Description:
198 VASTUS INTERMEDIUS The fibers of this muscle run at an angle of 50° to
55° to the longitudinal axis of the femur. The
Origin: muscle appears to bulge quickly with training and
Femur (anterior and lateral surfaces of upper 2 / 3 to atrophy with disuse before the other quadriceps
of shaft) show changes. This is deceiving because the
medialis oblique has the most sparse and thinnest
Lateral intermuscular septum (lower part) fascial investment, making changes in it more
obvious to observation.
Insertion:
Insertion (all):
Patella (base: into an anterior aponeurosis of mus- The tendons of the five heads unite at the distal thigh
cle that attaches to the middle part of the to form a common strong tendon (quadriceps
deep layer of the quadriceps tendon, and tendon) that inserts into the proximal margin of
then into the ligamentum patellae to insert into the patella. Fibers continue across the anterior
the tibial tuberosity) surface to become the patellar tendon (ligamentum
patellae), which inserts into the tuberosity of the
Description: tibia.
The deepest of the quadriceps muscles, this mus-
cle lies under the rectus femoris, the vastus Function (all):
medialis, and the vastus lateralis. It often appears Knee extension (none of the heads functions
inseparable from the medialis. It almost completely independently)
surrounds the proximal 2/3 of the shaft of the Hip flexion (by rectus femoris, which crosses the hip
femur. A small muscle, the articularis genus
occasionally is distinguishable from the joint)
intermedius, but more commonly it is part of the
intermedius. Innervation (all):
L2-L4 femoral nerve
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201 ARTICULARIS GENUS 208 Peroneus longus
Origin: 209 Peroneus brevis
Femur (shaft, lower anterior surface) 210 Peroneus tertius
Insertion: 203 TIBIALIS ANTERIOR
Knee joint (synovial membrane, upper part) Origin:
Tibia (lateral condyle and proximal 2 / 3 of lateral
Description: surface)
Interosseous membrane
This small muscle is mostly distinct, but it may be Deep surface of crural fascia
inseparable from the vastus intermedius. Intermuscular septum
Function: Insertion:
Retracts the synovial membrane during knee 1st (medial) cuneiform bone (on medial and plantar
extension, purportedly preventing this membrane surfaces)
from being entrapped between the patella and the 1st metatarsal bone (base)
femur
Description:
Innervation: Located on the lateral aspect of the tibia, the
L2-L4 femoral nerve muscle has a thick belly proximally but is
tendinous distally. The fibers drop vertically and
202 POPLITEUS end in a prominent tendon on the anterior surface
of the lower leg. The muscle is contained in
Origin: the most medial compartments of the extensor
Capsule of knee joint (by a strong tendon to lateral retinacula.
condyle of the femur)
Femur (lateral condyle, popliteal groove on anterior Function:
surface) Ankle dorsiflexion (talocrural joint)
Arcuate popliteal ligament Foot inversion and adduction (supination) at subtalar
Lateral meniscus of knee joint40 and midtarsal joints
Supports medial-longitudinal arch of foot in
Insertion: walking
Tibia (posterior triangular surface above soleal line)
Tendinous expansion of muscle Innervation
L4-L5 (often S1) deep peroneal nerve
Description:
Sweeps across the upper leg from lateral to medial 204 TIBIALIS POSTERIOR
just below the knee. Forms the lower floor of
the popliteal fossa. It is believed to protect Origin:
the lateral meniscus from a crush injury during Tibia (proximal 2/3 of posterior lateral shaft)
external rotation of the femur and flexion of the Fibula (proximal 2 / 3 of posterior medial shaft and
knee 40 head)
Interosseous membrane (entire posterior surface
Function: attachment except lower portion where flexor hallucis longus
Knee flexion originates)
Knee internal rotation (proximal Deep transverse fascia and intermuscular septa
fixed)
Insertion:
Hip external rotation (tibia fixed) Navicular bone (tuberosity)
Cuneiform bones (media, intermediate, lateral)
Innervation: Cuboid (slip)
L4-S1 tibial nerve (high branch)
2nd, 3rd, and 4th metatarsals (bases) (variable)
Muscles of the Ankle
Description:
203 Tibialis anterior Most deeply placed of the flexor group, high on
204 Tibialis posterior the posterior leg, this muscle is overlapped by
205 Gastrocnemius both the flexor hallucis longus and the flexor
206 Soleus digitorum longus. It ascends by two narrow heads
207 Plantaris and descends centrally on the leg, forming its
distal tendon in the distal 1 / 4 . This tendon passes
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behind the medial malleolus (with the flexor Innervation:
digitorum longus), enters the foot on the plantar S1-S2 tibial nerve
surface (where it contains a sesamoid bone), and
then divides to its several insertions. 206 SOLEUS
During weight bearing the tibialis posterior assists in
arch support and distribution of weight on the Origin:
foot to maintain balance. Fibula (head, posterior surface; shaft: proximal 1 /3
on posterior surface)
Function: Tibia (soleal line and middle 1 /3 of medial side of
shaft)
Foot inversion Fibrous arch between tibia and fibula
Aponeurosis (anterior aspect)
Ankle plantar flexion (accessory)
Insertion:
Innervation: nerve (low Aponeurosis over posterior surface of muscle, which,
L4-L5 (sometimes S1) tibial with tendon of gastrocnemius, thickens to become
branches) the tendo calcaneus
Calcaneus (posterior surface via tendo calcaneus along
205 GASTROCNEMIUS with gastrocnemius)41
Tendinous raphe in midline of muscle
Rises via two heads
Description:
Origin: This is a one-joint muscle, the largest of the
Medial bead: triceps surae. It is broad and flat and lies just
Femur (medial condyle, depression on upper under the gastrocnemius. Its anterior attachment
posterior part; popliteal surface adjacent to is a wide aponeurosis, and most of its
medial condyle) fibers course obliquely to the descending tendon
Capsule of knee joint on its posterior side. Below midcalf the soleus is
Aponeurosis wider than the tendon of the gastrocnemius and
Lateral bead: on both sides. It is, therefore, accessible for biopsy
and electrophysiological studies.
Femur (lateral condyle and posterior surface of The soleus is constantly active in quiet stance. It
shaft above lateral condyle; lower supracondylar responds to the forward center of mass to prevent
line) the body from tailing forward.
Capsule of knee joint Function:
Aponeurosis Ankle plantar flexion
Foot inversion
Insertion:
Calcaneus (via tendo calcaneus into middle posterior Innervation:
surface). Fibers of tendon rotate 90° such that S1-S2 tibial nerve
those associated with the gastrocnemius are
attached more laterally on the calcaneus. 207 PLANTARIS
Description: Origin:
The most superficial of the calf muscles, it gives Femur (supracondylar line, lateral)
the characteristic contour to the calf. It is a Oblique popliteal ligament of knee joint
two-joint muscle with two heads arising from
the condyles of the femur and descending to Insertion:
the calcaneus. The medial head is the larger, Tendo calcaneus (medial border) to calcaneum
and its fibers extend further distally before Plantar aponeurosis
spreading into a tendinous expansion, as does
the lateral head. The two heads join as the Description:
aponeurosis narrows and form the tendo calca- This small fusiform muscle lies between the
neus. The belly of the muscle extends to about gastrocnemius and the soleus. It is sometimes
midcalf (the medial head is the longer) before absent; at other times it is doubled. Its short belly
inserting into the aponeurosis. is followed by a long slender tendon of insertion
along the medial border of the tendo calcaneus
Function: and inserts with it on the posterior calcaneum.
Ankle plantar flexion
Knee flexion (accessory)
Foot eversion
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The plantaris is somewhat like the palmaris side of the calcaneus, passing forward to the 5th
longus in the hand and is of little function in metatarsal.
humans.41
Function:
Function: Foot eversion
Ankle plantar flexion (assist) Ankle plantar flexion (accessory)
Knee flexion (weak accessory)
Innervation:
Innervation: L5-S1 superficial peroneal nerve
S1-S2 tibial nerve (high branches)
210 PERONEUS TERTIUS
208 PERONEUS LONGUS
Origin:
Origin: Fibula (distal 1/3 of medial surface)
Fibula (head and upper 2 / 3 of lateral shaft) Interosseous membrane (anterior)
Tibia (lateral condyle, occasionally) Intermuscular septum
Deep crural fascia and intermuscular septa
Insertion:
Insertion: 5th metatarsal (dorsal surface of base; shaft: medial
1st metatarsal (lateral plantar side of base) aspect)
1st (medial) cuneiform (lateral plantar aspect)
2nd metatarsal (occasionally by a slip) Description:
This muscle is considered part of the extensor
Description: digitorum longus (i.e., the fifth tendon). The
Muscle is found proximally on the fibular side of muscle descends on the lateral leg, diving under
the leg where it is superficial to the peroneus the extensor retinaculum in the same passage as
brevis. The belly ends in a long tendon that the extensor digitorum longus, to insert on the
passes behind the lateral malleolus (with the fifth metatarsal. Muscle varies greatly.
brevis) and then runs obliquely forward lateral to
the calcaneus and crosses the plantar aspect of the Function:
foot to reach the first metatarsal and medial Ankle dorsiflexion
cuneiform. Foot eversion (accessory)
It maintains concavity of foot (along with brevis)
during toe-off and tiptoeing. Innervation:
L5-S1 deep peroneal nerve
Function:
Foot eversion Muscles Acting on the Toes
Ankle plantar flexion (assist)
Depression of 1st metatarsal 211 Extensor digitorum longus
Support of longitudinal and transverse arches
212 Extensor digitorum brevis
Innervation:
L5-S1 superficial peroneal nerve 213 Flexor digitorum longus
209 PERONEUS BREVIS 214 Flexor digitorum brevis
Origin: 215 Abductor digiti minimi
Fibula (shaft: distal 2 / 3 of lateral surface)
Intermuscular septa 216 Flexor digiti minimi brevis
Insertion: 217 Quadratus plantae (Flexor digitorum
5th metatarsal (tuberosity on lateral surface of accessorius)
base)
218 Lumbricales
Description:
The peroneus brevis lies deep to the longus and is 219 Interossei, dorsal (foot)
the shorter and smaller muscle of the two. The
belly fibers descend vertically to end in a ten- 220 Interossei, plantar
don, which courses (with the longus) behind
the lateral malleolus (the pair of muscles share 211 EXTENSOR DIGITORUM LONGUS
a synovial sheath). It bends forward on the lateral
Origin:
Tibia (lateral condyle on lateral side)
Fibula (shaft: upper 3/4 of medial surface)
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Interosseous membrane (anterior surface) Innervation:
Deep crural fascia and intermuscular septum L5-S1 deep peroneal nerve, lateral terminal branch
Insertion: 213 FLEXOR DIGITORUM LONGUS
Tendon of insertion divides into four tendon slips to
dorsum of foot that form an expansion over each Origin:
toe: Tibia (shaft: posterior surface of middle 2/3)
Toes 2 to 5: Fascia covering tibialis posterior
Middle phalanges (PIP joints) of the four lesser toes
(intermediate slip to dorsum of base of each) Insertion:
Distal phalanges (two lateral slips to dorsum of base
of each) Toes 2 to 5 (distal phalanges: base, plantar surface)
Description: Description:
Muscle lies in the lateral aspect of the anterior leg. Muscle lies deep on the tibial side of the leg and
It descends lateral to the tibialis anterior, and increases in size as it descends. The tendon of
its distal tendon accompanies the tendon of insertion extends almost the entire length of the
the peroneus tertius before dividing. It is attached muscle and is joined in the sole of the foot by
in the manner of the extensor digitorum of the the tendon of the quadratus plantae. It finally
hand. divides into four slips, which insert into the four
lateral toes.
Function:
MP extension of four lesser toes Function:
PIP and DIP extension (assist) of four lesser toes Toes 2 to 5: MP, PIP, and DIP flexion
Ankle dorsiflexion (accessory) Ankle plantar flexion (accessory)
Foot eversion (accessory) Foot inversion (accessory)
Innervation: Innervation:
L5-S1 deep peroneal nerve L5-S2 tibial nerve
212 EXTENSOR DIGITORUM BREVIS 214 FLEXOR DIGITORUM BREVIS
Origin: Origin:
Calcaneus (superior proximal surface anterolateral to Calcaneus (tuberosity, medial process)
the calcaneal sulcus) Intermuscular septa (adjacent)
Lateral talocalcaneal ligament Plantar aponeurosis (central part)
Extensor retinaculum (inferior)
Insertion:
Insertion: Toes 2 to 5 (by four tendons to middle phalanges,
Ends in four tendons: both sides)
(1) Hallux (proximal phalanx). This tendon is the
largest and most medial. It frequently is de- Description:
scribed as a separate muscle, the extensor hallucis This muscle is located in the middle of the sole of
brevis. the foot immediately above the plantar
(2, 3, 4) Three tendons join the tendon of extensor aponeurosis. It divides into four tendons, one for
digitorum longus (lateral surfaces). each of the four lesser toes. At the base of the
proximal phalanx each is divided into two slips,
Description: which encircle the tendon of the flexor digitorum
The muscle passes medially and distally across the longus. The tendons divide a second time and
dorsum of the foot to end in four tendons, one insert onto both sides of the middle phalanges.
to the hallux and three to toes 2, 3, and 4. Varies The pattern of insertion is the same as that for
considerably. the tendons of the flexor digitorum superficialis
in the hand.
Function:
Hallux (great toe): MP extension Function:
Toes 2 to 4: MP extension Toes 2 to 5 MP and PIP flexion
Toes 2 to 4: IP extension (assist)
Innervation:
S1-S2 medial plantar nerve
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215 ABDUCTOR DIGITI Medial head:
MINIMI (Foot) Calcaneus (medial concave surface)
Long plantar ligament (medial border)
Origin:
Calcaneus (tuberosity, medial and lateral processes) Insertion:
Plantar aponeurosis and intermuscular septum Tendon of flexor digitorum longus (lateral margin)
may fuse with long flexor tendon.42
Insertion:
Toe 5 (base of proximal phalanx, lateral aspect) Description:
Insertion is in common with flexor digiti minimi This muscle is sometimes known as the flexor
brevis digitorum accessorius, or just flexor
accessorius.
Description:
Lies along the lateral border of the foot and in- The medial head is larger, whereas the lateral head
serts in common with the flexor digiti minimi is more tendinous. They rise from either side of
brevis. Its insertion on the lateral side of the base the calcaneus, pass medially, and join in an acute
of the 5th toe makes it as much a flexor as an angle at midfoot, to end in the lateral margin of
abductor. the tendon of the flexor digitorum longus. Muscle
may be absent.
Function:
Toe 5 abduction Function:
Toe 5 MP flexion Toes 2 to 5 D I P flexion (in synergy with the flexor
digitorum longus)
Innervation:
S1-S3 lateral plantar nerve Innervation:
S1-S3 lateral plantar nerve
216 FLEXOR DIGITI MINIMI BREVIS
218 LUMBRICALES (Foot)
Origin:
5th metatarsal (base, plantar surface) These are four small muscles considered accessories
Sheath of peroneus longus to the flexor digitorum longus.
Insertion: Origin:
1st lumbrical: Originates by a single head from the
Toe 5 (proximal phalanx, lateral aspect of base) medial side of the tendon of the flexor digitorum
longus bound for toe 2.
Description: 2nd, 3rd, and 4th lumbricales: Originate by dou-
Muscle lies superficial to the 5th metatarsal and ble heads from adjacent sides of tendons of the
looks like an interosseous muscle. Sometimes flexor digitorum longus bound for toes 3, 4,
fibers are inserted into the lateral distal half of and 5.
the 5th metatarsal, and these have been de-
scribed as a distinct muscle called the opponens Insertion (all):
digiti minimi. Toes 2 to 5 (proximal phalanges and dorsal
expansions of the tendons of extensor digitorum
Function: longus)
Toe 5 MP flexion
Description:
Innervation:
S2-S3 lateral plantar nerve (superficial branch) The lumbricales are four small muscles intrinsic
to the foot. They are numbered from the me-
217 QUADRATUS PLANTAE (Flexor dial (hallux) side of the foot; therefore the 1st
lumbrical goes to toe 2 and the 4th lumbrical goes
Digitorum Accessorius) to toe 5.
Rises via two heads Function:
Toes 2 to 5: MP flexion
Origin: Toes 2 to 5: PIP and D I P extension (assist)
Lateral head:
Calcaneus (lateral border distal to lateral process Innervation: plantar nerve plantar
of tuberosity) First lumbrical: L 5 - S 1 medial S2-S3 lateral
Long plantar ligament 2nd, 3rd, and 4th lumbricales:
nerve, deep branch
Chapter 9 / Ready Reference Anatomy 4 2 5
Part 3. Skeletal Muscles of the Human Body
219 DORSAL INTEROSSEI (Foot) them. Each connects with only one metatarsal.
As with the dorsal interossei, the muscles are
There are four dorsal interossei. innervated by the deep branch of the lateral
plantar nerve, except for the 3rd plantar muscle,
Origin: which lies in the 4th interosseous space and is
Metatarsal bones (each head arises from the adjacent innervated by the superficial branch of the same
sides of the metatarsal bones between which it nerve.
lies)
Function:
Insertion: Toes 3, 4, and 5: Adduction (toward the axis of
1st dorsal: T o e 2 proximal phalanx, medial side of toe 2)
base MP flexion
2nd dorsal: T o e 2 proximal phalanx, lateral side of IP extension (assist)
base
3rd dorsal: T o e 3 proximal phalanx, lateral side of Innervation:
base 1st and 2nd plantars: S 2 - S 3 lateral plantar nerve
4th dorsal: T o e 4 proximal phalanx, lateral side of (deep branch)
base 3rd plantar: S 2 - S 3 lateral plantar nerve (superficial
All: Tendons of extensor digitorum longus via dorsal branch)
digital expansion
Muscles Acting on the Great Toe
Description:
The dorsal interossei are four bipennate muscles, 221 Extensor hallucis longus
each arising by two heads. They are similar to
the interossei of the hand except that their action 222 Flexor hallucis longus
is considered relative to the midline of the
2nd digit (the longitudinal axis of the foot). 223 Flexor hallucis brevis
The muscles are innervated by the lateral plan-
tar nerve, deep branch, except for the 4th 224 Abductor hallucis
dorsal muscle that lies in the 4th interosseous
space; it is supplied by the superficial branch of 225 Adductor hallucis
the same nerve.
221 EXTENSOR HALLUCIS LONGUS
Function:
foes 2 to 4: Abduction from longitudinal axis of Origin:
foot, which lines up through toe 2 Fibula (shaft: medial aspect of middle half)
Toes 2 to 4: MP flexion (accessory) Interosseous membrane
Toes 2 to 4: IP extension (possibly)
Insertion:
Innervation: Hallux (base of distal phalanx, dorsal surface)
1st, 2nd, and 3rd dorsals: S 2 - S 3 lateral plantar nerve, Expansion to base of proximal phalanx of hallux
deep branch
4th dorsal: S 2 - S 3 lateral plantar nerve, superficial Description:
branch (1st dorsal also may receive a slip from This thin muscle travels lateral to medial as it descends
the deep peroneal, medial branch; the 2nd dor- the leg between and largely covered by the tibialis
sal may receive a slip from the deep peroneal, anterior and the extensor digitorum longus. Its
lateral branch) tendon does not emerge superficially until it
reaches the distal 1/3 of the leg. It may be joined
220 PLANTAR INTEROSSEI with the extensor digitorum longus.
Origin: Function:
3rd, 4th, and 5th metatarsal bones (bases and medial Hallux: MP and IP extension
sides) Ankle dorsiflexion (accessory)
Foot inversion (accessory)
Insertion:
Proximal phalanges of same toe (bases and medial Innervation:
sides) L5 deep peroneal nerve
L4-S1 also cited
Dorsal digital expansion
222 FLEXOR HALLUCIS LONGUS
Description:
These are three muscles that lie along the plantar Origin:
surface of the metatarsals rather than between Fibula (shaft: inferior 2/3 of posterior surface)
4 2 6 Chapter 9 / Ready Reference Anatomy
Part 3. Skeletal Muscles of the Human Body
Interosseous membrane Insertion:
Posterior crural intermuscular septum Hallux (base of proximal phalanx, medial side)
Fascia over tibialis posterior Medial sesamoid of hallux
Joins tendon of flexor hallucis brevis
Insertion:
Hallux (distal phalanx at base on plantar surface) Description:
Slip to tendon of flexor digitorum longus This muscle lies along the medial border of the foot.
Its tendon attaches distally to the medial tendon
Description: of the flexor hallucis brevis, and they insert
together on the hallux.
This muscle lies deep in the lateral side of the leg. When fibers from the muscle are attached to the first
Its fibers pass obliquely down via a long tendon metatarsal, it can be considered an opponens
that runs along the whole length of its posterior hallucis
surface and then crosses over the distal end of the
tibia, talus, and the inferior surface of the Function:
calcaneus. It then runs forward on the sole of the Hallux abduction (away from toe 2)
foot to the distal phalanx of the hallux. Hallux MP flexion (accessory)
Function: foot inversion Innervation:
Hallux IP flexion S1-S2 medial plantar nerve
Hallux MP flexion (accessory)
Ankle plantar flexion and 225 ADDUCTOR HALLUCIS
(accessory)
Arises from two heads
Innervation:
L5-S2 tibial nerve (low branches) Origin:
Oblique head:
223 FLEXOR HALLUCIS BREVIS Second, third, and fourth metatarsals (bases)
Sheath of peroneus longus tendon
Origin: Transverse head:
Toes 3 to 5: Plantar metatarsophalangeal liga-
Lateral part: ments
Cuboid (medial part of plantar surface) Deep transverse metatarsal ligaments between toes
Cuneiform (lateral)
Insertion:
Medial part: Oblique:
Tendon of tibialis posterior Hallux (base of proximal phalanx, lateral aspect)
Medial intermuscular septum Lateral sesamoid bone of hallux
Blends with flexor hallucis brevis
Insertion: Transverse:
Hallux: Sides of base of proximal phalanx Proximal phalanx of hallux (debated)
The medial part blends with the abductor hallucis. Lateral sesamoid of hallux
The lateral part blends with adductor hallucis.
Description:
Description: The two heads are unequal in size, the oblique
One of the muscles of the third layer (of four layers) being the larger and more muscular. It is lo-
of plantar muscles. It is located adjacent to the cated in the third layer of plantar muscles. The
plantar surface of the 1st metatarsal. oblique head crosses the foot from center to
medial on a long oblique axis; the transverse
Function: head courses transversely across the metatar-
Hallux abduction (away from toe 2) sophalangeal joints.
Hallux MP flexion
Function:
Innervation: Hallux adduction (toward toe 2)
S1-S2 medial plantar nerve Hallux MP flexion (accessory)
Support of transverse metatarsal arch
224 ABDUCTOR HALLUCIS
Innervation:
Origin: S2-S3 lateral plantar nerve, deep branch
Flexor retinaculum
Calcaneus (tuberosity, medial process)
Plantar aponeurosis and intermuscular septum
Chapter 9 / Ready Reference Anatomy 4 2 7
PART 4. MOTIONS AND THEIR PARTICIPATING MUSCLES (MOTIONS OF
THE NECK, TRUNK, AND LIMBS)
In this part of the ready reference chapter, each mo- the literature. We have used the American and British
tion of the axial skeleton and trunk is listed along (primarily) versions of Gray's Anatomy as the princi-
with the muscles that participate in that motion re- pal references, but occasionally kinesiologic impera-
gardless of the extent of their contribution. tives have caused us to deviate from orthodoxy for
some muscles.
As with all aspects of human anatomy, widely dif-
ferent opinions about functional anatomy are cited in
MOTIONS OF THE CERVICAL 66. Iliocostalis cervicis C4-T3
SPINE AND HEAD
67. Splenius cervicis C4-C8
Note: The small muscles of the neck are variably in- 69. Interspinales cervicis C3-C8
nervated.
68. Spinalis cervicis C4-C8
Capital Extension (All muscles act bilaterally)
124. Trapezius (upper) Accessory (XI)
56. Rectus capitis posterior C1 (suboccipital) and C 3 - C 4
major
70. Intertransversarii cervicis C 3 - C 8
57. Rectus capitis posterior C1(suboccipital) 71. Rotatores cervicis C3-C8
minor 94. Multifidus Segmental spinal
nerves (axis to
58. Obliquus capitis superior C1 (suboccipital) 127. Levator scapulae sacrum)
59. Obliquus capitis inferior C1 (suboccipital) C 3 - C 4 spinal
(extension doubtful) nerves (ventral
rami)
60. Longissimus capitis C3-C8 (greater
occipital) C5 dorsal
scapular nerve
61. Splenius capitis C3-C6
62. Semispinalis capitis C2-T1 Cervical Flexion (All muscles act
bilaterally and are variable)
63. Spinalis capitis C3-T1
79. Longus colli C2-C6
83. Sternocleidomastoid Accessory (XI) 80. Scalenus anterior C4-C6
(posterior) and C 2 - C 3 81. Scalenus medius C3-C8
82. Scalenus posterior C6-C8
124. Trapezius (upper) Accessory (XI) 83. Sternocleidomastoid Accessory (XI),
C2-C3
and C 3 - C 4 84. Sternothyroid C1-C3
85. Thyrohyoid Hypoglossal (XII)
Capital Flexion (All muscles act bilaterally) 86. Sternohyoid and C1
Hypoglossal (XII)
72. Rectus capitis anterior C 1 - C 2 87. Omohyoid and C 1 - C 3
88. Platysma C1-C3
73. Rectus capitis lateralis C1-C2 Facial (VII)
74. Longus capitis C1-C3
75. Mylohyoid Trigeminal (V)
76. Stylohyoid Facial (VII)
77. Geniohyoid Hypoglossal (XII)
with fibers from C1
78. Digastric
Anterior belly Trigeminal (V)
Posterior belly Facial (VII)
Cervical Extension (All muscles act bilaterally) Lateral Bending (Ear to shoulder)
64. Longissimus cervicis C3-T3 The muscles used in this movement are the capital
65. Semispinalis cervicis C2-T5 extensors and flexors on that side, and the cervical
flexors and extensors on that side.
4 2 8 Chapter 9 / Ready Reference Anatomy
Part 4. Motions and Their Participating Muscles (Motions of the Neck, Trunk, and Limbs)
Rotation to Same Side (Turn face MOTIONS OF THE LUMBAR
to same side; all variable) SPINE AND PELVIS
56. Rectus capitis posterior C1 (suboccipital) Lumbar Forward Flexion
major
59. Obliquus capitis inferior C1 (suboccipital) 110. Obliquus externus T7-T12
abdominis (both) T7-L1
60. Longissimus capitis C3-C8 T7-T12
111. Obliquus internus L2-L4
61. Splenitis capitis C3-C6 abdominis (both) L1
(debated)
113. Rectus abdominis
67. Splenitis cervicis C4-C8 (both)
74. Longus capitis C1-C3 174. Psoas major
80. Scalenus anterior C4-C6 175. Psoas minor
81. Scalenus medius C3-C8
82. Scalenus posterior C6-C8 Lumbar Extension
127. Levator scapulae C5 (dorsal
scapular) and 90. Iliocostalis lumborum L1-L5
C3-C4 (both)
Rotation to Opposite Side 94. Multifidus Spinal nerves: axis
(All innervations variable) to sacrum
124. Trapezius (upper) Accessory (XI) 96. Rotatores lumborum Lumbar spinal
and C 3 - C 4 (both) nerves (variable)
62. Semispinalis capitis
65. Semispinalis cervicis C2-T1 98. Interspinales lumborum Lumbar spinal
71. Rotatores cervicis nerves (variable)
79. Longus colli C2-T5
83. Sternocleidomastoid 99. Intertransversarii Thoracic and
C3-C8 thoracis and lumborum lumbar spinal
94. Multifidus nerves
C2-C6 (dorsal rami)
Accessory (XI) and 100. Quadratus lumborum T12-L3
C2-C3 (both) (ventral rami)
Segmental spinal
nerves 182. Gluteus maximus L5-S2 inferior
gluteal nerve
MOTIONS OF THE THORACIC SPINE Lumbar Lateral Bending
Thoracic Extension 90. Iliocostalis lumborum Lumbar spinal
nerves (variable)
89. Iliocostals thoracis T 1 - T 1 2 (variable) 99. Intertransversarii Lumbar spinal
91. Longissimus thoracis lumborum nerves (variable)
92. Spinalis thoracis Tl-Ll T12-L3
93. Semispinalis thoracis 100. Quadratus lumborum T7-T12
94. Multifidus T 1 - T 1 2 (variable) 110. Obliquus externus
T7-L1
95. Rotatores thoracis T1-T12 abdominis
97. Interspinales thoracis 111. Obliquus internus L2-L4
T 1 - T 1 2 spinal
99. Intertransversarii abdominis
thoracis nerves; whole spine 174. Psoas major
T 1 - T 1 2 (variable) Lumbar Rotation to Same Side
T1-T3, T11-T12 111. Obliquus internus abdominis T7-L1
(variable)
Thoracic spinal
nerves (very
variable)
Chapter 9 / Ready Reference Anatomy 4 2 9
Part 4. Motions and Their Participating Muscles (Motions of the Neck, Trunk, and Limbs)
Lumbar Rotation to Opposite Side Forced Inspiration
94. Multifidi Spinal nerves, axis All muscles of quiet inspiration plus:
to sacrum
96. Rotatores lumborum 83. Sternocleidomastoid Accessory (XI);
Lumbar spinal C2-C3
110. Obliquus externus nerves (variable)
abdominis 88. Platysma Facial (VII)
T7-T12
131. Pectoralis major C5-T1 (medial
and lateral
pectorals)
MOTIONS OF RESPIRATION 129. Pectoralis minor C5-T1 (medial
and lateral
pectorals)
Quiet Inspiration 130. Latissimus dorsi C6-C8
101. Diaphragm C4 (phrenic) (thoracodorsal)
102. Intercostales externi
Tl-Tll Elevation of Pelvis
103. Intercostales interni (intercostal)
100. Quadratus lumborum T 1 2 - L 3 spinal
104. Intercostales intimi T1-T11 nerves
(intercostal) 130. Latissimus dorsi C6-C8
107. Levatores costarum (thoracodorsal)
Tl-Tll 110. Obliquus externus
80. Scalenus anterior (intercostal) abdominis T 7 - T 1 2 spinal
81. Scalenus medius nerves
82. Scalenus posterior Tl-Tll 111. Obliquus internus
108. Serratus posterior abdominis T 7 - T 1 2 spinal
(intercostal) nerves
superior 90. Iliocostalis lumborum
Deep back, extensors C4-C6 L 1 - L 5 spinal
nerves
C3-C8
UPPER EXTREMITY MOTIONS
C6-C8
T2-T5
(intercostal)
Segmental spinal
nerves
Expiration (During exertion, coughing, Valsalva The Scapula
maneuver, etc.)
Scapular Elevation (Shrugging)
110. Obliquus externus T7-T12 124. Trapezius (upper) Accessory (XI) and
abdominis 127. Levator scapulae C3-C4
125. Rhomboid major
111. Obliquus interims T7-L1 126. Rhomboid minor C 3 - C 4 ; C5 (dorsal
abdominis scapular)
Scapular Depression
113. Rectus abdominis T7-T12 C5 (dorsal
scapular)
112. Transversus abdominis T 7 - L 1 (intercostal)
C5 (dorsal
102. Intercostales externi Tl-Tll
scapular)
(supporting data scarce) (intercostal)
103. Intercostales interni Tl-Tll
(intercostal)
106. Transversus thoracis T2-T11 124. Trapezius (lower) Accessory (XI) and
(intercostal) 132. Subclavius
C3-C4
130. Latissimus dorsi C6-C8 C5-C6 (nerve to
(thoracodorsal) subclavius)
4 3 0 Chapter 9 / Ready Reference Anatomy
Part 4. Motions and Their Participating Muscles (Motions of the Neck, Trunk, and Limbs)
Scapular Abduction (Protraction) Shoulder Adduction
130. Latissimus dorsi
128. Serratus anterior C5-C7 (long 131. Pectoralis major C6-C8
129. Pectoralis minor thoracic) (thoracodorsal)
137. Teres minor
C5-T1 (medial 138. Teres major C5-T1 (medial
pectoral) 139. Coracobrachialis and lateral
pectorals)
Scapular Adduction (Retraction)
C5-C6
124. Trapezius (middle and Accessory (XI) and (axillary)
lower) C3-C4
C5-C6
125. Rhomboid major C5 (dorsal (subscapular)
scapular)
126. Rhomboid minor C5-C7
C5 (dorsal (musculocutaneous)
127. Levator scapulae scapular)
Shoulder Internal Rotation (Medial rotation)
C 3 - C 4 ; C5 (dorsal
scapular) 130. Latissimus dorsi C6-C8
131. Pectoralis major (thoracodorsal)
Scapular Upward Rotation (Glenoid fossa up)
134. Subscapularis C5-T1 (medial
124. Trapezius (upper and Accessory (XI) 138. Teres major and lateral
lower) and C 3 - C 4 133. Deltoid (anterior) pectorals)
128. Serratus anterior C5-C7 (long C5-C6
thoracic) (subscapular)
Scapular Downward Rotation C5-C6
(Glenoid fossa down) (subscapular)
C 5 - C 6 (axillary)
125. Rhomboid major C5 (dorsal Shoulder Horizontal Adduction
126. Rhomboid minor scapular)
127. Levator scapulae 131. Pectoralis major C5-T1 (medial
C5 (dorsal 133. Deltoid (anterior) and lateral
scapular) pectorals)
C 3 - C 4 ; C5 (dorsal C 5 - C 6 (axillary)
scapular)
The Shoulder (Glenohumeral Motions) Shoulder Horizontal Abduction
Shoulder Flexion 133. Deltoid (posterior) C 5 - C 6 (axillary)
139. Coracobrachialis C5-C7 Shoulder External Rotation (Lateral rotation)
(musculocutaneous)
133. Deltoid (anterior and C 5 - C 6 (axillary) 133. Deltoid (posterior) C 5 - C 6 (axillary)
middle) 136. Infraspinatus
C 5 - C 6 (lateral C5-C6
131. Pectoralis major pectoral) 137. Teres minor (suprascapular)
(clavicular part)
C 5 - C 6 (axillary)
Shoulder Abduction C 5 - C 6 (axillary) Shoulder Extension C6-C8
130. Latissimus dorsi (thoracodorsal)
133. Deltoid (middle) C5-C6 133. Deltoid (posterior)
135. Supraspinatus (suprascapular) C 5 - C 6 (axillary)
Chapter 9 / Ready Reference Anatomy 4 3 1
Part 4. Motions and Their Participating Muscles (Motions of the Neck, Trunk, and Limbs)
138. Teres major C5-C7 166. Abductor pollicis longus C 7 - C 8 (radial)
(subscapular)
142. Triceps brachii 169. Flexor pollicis longus C7-C8 (median)
(long head) C6-C8 (radial)
152. Palmaris longus C7-C8 (median)
Wrist Extension
Elbow and Forearm Motions 148. Extensor carpi radialis C 6 - C 7 (radial)
longus
Elbow Flexion C 7 - C 8 (radial)
149. Extensor carpi radialis
140. Biceps brachii C5-C6 brevis C 7 - C 8 (radial)
(musculocutaneous) C 7 - C 8 (radial)
141. Brachialis C5-C6 150. Extensor carpi ulnaris C 7 - C 8 (radial)
(musculocutaneous) C 7 - C 8 (radial)
143. Brachioradialis C 5 - C 6 (radial) 154. Extensor digitorum
146. Pronator teres C6-C7 (median)
148. Extensor carpi radialis C6-C7 (radial) 158. Extensor digiti minimi
longus C6-C7 (median) 155. Extensor indicis
151. Flexor carpi radialis C7-C8 (median)
152. Palmaris longus C7-T1 (ulnar) Wrist Radial Deviation (Abduction)
153. Flexor carpi ulnaris
148. Extensor carpi radialis C6-C7 (radial)
longus
149. Extensor carpi radialis C 7 - C 8 (radial)
brevis
Elbow Extension 151. Flexor carpi radialis C6-C7 (median)
142. Triceps brachii C6-C8 (radial) 167. Extensor pollicis longus C 7 - C 8 (radial)
144. Anconeus C6-C8 (radial)
168. Extensor pollicis brevis C 7 - C 8 (radial)
166. Abductor pollicis longus C 7 - C 8 (radial)
Forearm Pronation C6-C7 (median) Wrist Ulnar Deviation (Adduction)
C7-C8 (median)
146. Pronator teres C6-C7 (median) 150. Extensor carpi ulnaris C7-C8 (radial)
147. Pronator quadratus 153. Flexor carpi ulnaris C7-T1 (ulnar)
151. Flexor carpi radialis
Forearm Supination Thumb Motions
145. Supinator C6-C7 (radial) Thumb Flexion
140. Biceps brachii
C5-C6
(musculocutaneous) Carpometacarpal (CMC)
Wrist and Hand Motions 169. Flexor pollicis longus C7-C8 (median)
C8-T1 (median)
Wrist Flexion 172. Opponens pollicis
C8-T1 (median)
151. Flexor carpi radialis C6-C7 (median) 170. Flexor pollicis brevis: C8-T1 (ulnar)
C7-T1 (ulnar) Superficial head
153. Flexor carpi ulnaris C8-T1 (median) Deep head C8-T1 (median)
C8-T1 (ulnar)
156. Flexor digitorum C8-T1 (median) Metacarpophalangeal (MP) C7-C8 (median)
superficialis C8-T1 (ulnar) C8-T1 (ulnar)
170. Flexor pollicis brevis:
157. Flexor digitorum Superficial head
profundus: Deep head
Digits 2 and 3
Digits 4 and 5 169. Flexor pollicis longus
173. Adductor pollicis
4 3 2 Chapter 9 / Ready Reference Anatomy
Part 4. Motions and Their Participating Muscles (Motions of the Neck, Trunk, and Limbs)
Interphalangeal (IP) C7-C8 (median) Finger Motions: Digit 2, 3, and 4
169. Flexor pollicis longus (Index, Long, and Ring Fingers)
Thumb Extension Finger Flexion
Carpometacarpal (CMC) Metacarpophalangeal (MP) C8-T1 (median)
168. Extensor pollicis brevis C 7 - C 8 (radial) C8-T1 (median)
167. Extensor pollicis longus C 7 - C 8 (radial) 163. Lumbricales, 1st and C8-T1 (ulnar)
166. Abductor pollicis longus C 7 - C 8 (radial) 2nd, for digits 2 C8-T1 (ulnar)
and 3 C8-T1 (median)
Metacarpophalangeal (MP) C8-T1 (median)
168. Extensor pollicis brevis C 7 - C 8 (radial) 163. Lumbricales, 3rd and C8-T1 (ulnar)
167. Extensor pollicis longus C 7 - C 8 (radial) 4th, for digits 4
and 5
Interphalangeal (IP)
167. Extensor pollicis longus C 7 - C 8 (radial) 165. Palmar interossei for
171. Abductor pollicis brevis C 8 - T 1 (median) digits 2, 4, and 5
Thumb Abduction (Away 164. Dorsal interossei for
from digit 2 (index finger)) digits 2, 3, and 4
Carpometacarpal (CMC) 156. Flexor digitorum
superficialis for digits
166. Abductor pollicis C7-C8 (radial) 2 to 5
longus
157. Flexor digitorum
profundus for digits
2 and 3
157. Flexor digitorum
profundus for digits
4 and 5
168. Extensor pollicis brevis C 7 - C 8 (radial) Proximal Interphalangeal (PIP)
171. Abductor pollicis brevis C 8 - T 1 (median) 156. Flexor digitorum C8-T1 (median)
superficialis
172. Opponens pollicis C8-T1 (median)
152. Palmaris longus C7-C8 (median) 157. Flexor digitorum
profundus:
Metacarpophalangeal (MP) For digits 2 and 3 C8-T1 (median)
171. Abductor pollicis brevis C 8 - T 1 (median) For digits 4 and 5 C8-T1 (ulnar)
Thumb Adduction (Toward digit 2) Distal Interphalangeal (DIP)
Carpometacarpal (CMC) C8-T1 (ulnar) 157. Flexor digitorum C8-T1 (median)
173. Adductor pollicis C8-T1 (ulnar) profundus: C8-T1 (ulnar)
164. 1st dorsal interosseous For digits 2 and 3
For digits 4 and 5
Finger Extension
Metacarpophalangeal (MP) C8-T1 (ulnar) Metacarpophalangeal (MP) C7-C8 (radial)
173. Adductor pollicis C 7 - C 8 (radial)
154. Extensor digitorum
Thumb Opposition (Combination of internal (digits 2 to 5)
rotation, abduction, and flexion)
155. Extensor indicis
(digit 2)
172. Opponens pollicis C8-T1 (median)
C8-T1 (ulnar)
frequently Proximal and Distal Interphalangeal
(PIP and DIP)
171. Abductor pollicis brevis C 8 - T 1 (median) 154. Extensor digitorum C7-C8 (radial)
(digits 2 to 5)
170. Flexor pollicis brevis:
Superficial head C8-T1 (median) 155. Extensor indicis C 7 - C 8 (radial)
Deep head C8-T1 (ulnar) (digit 2)
Chapter 9 / Ready Reference Anatomy 4 3 3
Part 4. Motions and Their Participating Muscles (Motions of the Neck, Trunk, and Limbs)
163. Lumbricales: Distal Interphalangeal (DIP)
1st and 2nd,
for digits 2 and 3 C8-T1 (median) 157. Flexor digitorum C8-T1 (ulnar)
3rd and 4th, C8-T1 (ulnar) profundus for digit 5
for digits 4 and 5 C8-T1 (ulnar)
C8-T1 (ulnar) Extension (Digit 5)
165. Palmar interossei for
digits 2, 4, and 5 C8-T1 (ulnar) Metacarpophalangeal (MP)
154. Extensor digitorum
164. Dorsal interossei for C7-C8 (radial) 158. Extensor digiti minimi C 7 - C 8 (radial)
digits 2, 3, and 4 C 7 - C 8 (radial)
C8-T1 (ulnar)
Finger Abduction C7-C8 (radial) Proximal and Distal Interphalangeal
(PIP and DIP)
164. Dorsal interossei:
1st and 2nd, 154. Extensor digitorum C 7 - C 8 (radial)
for digits 2 and 3
3rd and 4th, 158. Extensor digiti minimi C 7 - C 8 (radial)
for digits 3 and 4
163. 4th lumbrical C8-T1 (ulnar)
154. Extensor digitorum
(digits 2, 4, and 5) 165. 3rd palmar interosseus C 8 - T 1 (ulnar)
Finger Adduction Abduction (Digit 5)
165. Palmar interossei: 154. Extensor digitorum C 7 - C 8 (radial)
1st, 2nd, and for 5th digit
3rd, for digits
2, 4 , and 5 159. Abductor digiti minimi C 8 - T 1 (ulnar)
155. Extensor indicis 158. Extensor digiti minimi C 7 - C 8 (radial)
(for index finger)
161. Opponens digiti minimi C 8 - T 1 (ulnar)
Adduction (Digit 5)
Finger Motion: Little Finger 165. 3rd palmar interosseus C 8 - T 1 (ulnar)
Flexion (Digit 5) Opposition (Digit 5)
Carpometacarpal (CMC) 159. Abductor digiti minimi C 8 - T 1 (ulnar)
161. Opponens digiti minimi C 8 - T 1 (ulnar)
161. Opponens digiti minimi C 8 - T 1 (ulnar)
Metacarpophalangeal (MP) 160. Flexor digiti minimi C8-T1 (ulnar)
brevis
160. Flexor digiti minimi C8-T1 (ulnar)
brevis 163. 4th lumbrical C8-T1 (ulnar)
C8-T1 (ulnar)
159. Abductor digiti minimi C8-T1 (ulnar) 165. 3rd palmar interosseus C 8 - T 1 (ulnar)
C8-T1 (ulnar)
163. 4th lumbrical C8-T1 (median) LOWER EXTREMITY MOTIONS
165. 3rd palmar interosseus C8-T1 (ulnar) Hip Motions
156. Flexor digitorum Hip Flexion
superficialis for digit 5
157. Flexor digitorum
profundus for digit 5
Proximal Interphalangeal (PIP) 176. Iliacus L2-L3 (femoral)
174. Psoas major L2-L4 (often L1)
156. Flexor digitorum C8-T1 (median) 196. Rectus femoris L2-L4 (femoral)
superficialis 195. Sartorius L2-L3 (femoral)
157. Flexor digitorum C8-T1 (ulnar)
profundus for digit 5
4 3 4 Chapter 9 / Ready Reference Anatomy
Part 4. Motions and Their Participating Muscles (Motions ot the Neck, Trunk, and Limbs)
177. Pectineus L2-L3 (femoral) 180. Adductor brevis L2-L3 (obturator)
179. Adductor longus L2 or L3-L4 179. Adductor longus
(obturator) L2 or L3-L4
180. Adductor brevis L2-L4 (obturator) 177. Pectineus (obturator)
181. Adductor magnus L2-L4 (obturator) 178. Gracilis
188. Obturator externus L2-L3 (femoral)
(superior) L4-S1 (superior 182. Gluteus maximus
185. Tensor fasciae latae gluteal) L2-L3 (obturator)
L4-S1 (lower)
183. Gluteus medius (superior gluteal) L3-L4 (obturator)
(anterior) L5-S2 (inferior
gluteal)
Hip Extension
Hip Internal Rotation (Medial rotation)
182. Gluteus maximus L5-S2 (inferior 183. Gluteus medius L4-S1 (superior
gluteal) (anterior) gluteal)
192. Biceps femoris (long)
L5-S2 (sciatic 184. Gluteus minimus L4-S1 (superior
193. Semitendinosus [tibial]) gluteal)
185. Tensor fasciae latae
194. Semimembranosus L5-S2 (sciatic L4-S1 (superior
[tibial]) 194. Semimembranosus gluteal)
181. Adductor magnus
(inferior) L5-S2 (sciatic 193. Semitendinosus L5-S2 (sciatic
[tibial]) [tibial])
183. Gluteus medius 181. Adductor magnus33
(posterior) L2-L4 (sciatic L5-S2 (sciatic
[tibial]) 179. Adductor longus [tibial])
Hip Abduction
L4-S1 (superior L2-L4 (obturator,
gluteal) sciatic | tibial ])
L2 or L3-L4
(obturator)
183. Gluteus medius L4-S1 (superior Hip External Rotation (Lateral rotation)
gluteal)
184. Gluteus minimus 182. Gluteus maximus L5-S2 (inferior
L4-S1 (superior
185. Tensor fasciae latae gluteal) gluteal)
195. Sartorius L4-S1 (superior 188. Obturator externus L3-L4 (obturator)
182. Gluteus maximus gluteal)
191. Quadratus femoris L5-S1 (nerve to
(upper) L2-L3 (femoral) 189. Gemellus superior quadratus femoris)
186. Piriformis (hip flexed) 190. Gemellus inferior L5-S1 (nerve to
L5-S2 (inferior obturator internus)
189. Gemellus superior gluteal) 187. Obturator internus L5-S1 (nerve to
(hip flexed) quadratus femoris)
S1-S2 (nerve to
190. Gemellus inferior piriformis) L5-S1 (nerve to
(hip flexed) obturator internus)
L5-S1 (nerve to
187. Obturator internus obturator internus) 186. Piriformis S1-S2 (nerve to
(hip flexed) piriformis)
L5-S1 (nerve to
Hip Adduction quadratus femoris) 195. Sartorius L2-L3 (femoral)
L5-S1 (nerve to 192. Biceps femoris (long) L5-S2 (sciatic
obturator internus) [tibial])
183. Gluteus medius
(posterior) L4-S1 (superior
gluteal)
181. Adductor magnus L2-L4 (sciatic 174. Psoas major L2-L4
[tibial] and
obturator) 202. Popliteus (tibia fixed) L4-S1 (tibial)
Chapter 9 / Ready Reference Anatomy 4 3 5
Part 4. Motions and Their Participating Muscles (Motions of the Neck, Trunk, and Limbs)
Knee Motions Short head L5-S2 (sciatic,
Knee Flexion 185. Tensor fasciae latae common peroneal)
194. Semimembranosus L5-S2 (sciatic L4-S1 (superior
[tibial]) gluteal)
193. Semitendinosus L5-S2 (sciatic Ankle and Foot Motions
[tibial])
Ankle Plantar Flexion
192. Biceps femoris:
Long L5-S2 (sciatic 205. Gastrocnemius S1-S2 (tibial)
[tibial]) 206. Soleus
Short L5-S2 (sciatic, 204. Tibialis posterior S1-S2 (tibial)
common peroneal) 208. Peroneus longus
L4-L5 (tibial)
178. Gracilis L2-L3 (obturator) 209. Peroneus brevis
L5-S1 (superficial
195. Sartorius L2-L3 (femoral) 207. Plantaris peroneal)
222. Flexor hallucis longus
202. Popliteus L4-S1 (tibial) 213. Flexor digitorum L5-S1 (superficial
peroneal)
185. Tensor fasciae latae L4-S1 (superior longus
(via iliotibial band) gluteal) S1-S2 (tibial)
(after 30° knee flexion)
L5-S2 (tibial)
207. Plantaris S1-S2 (tibial) L5-S2 (tibial)
205. Gastrocnemius S1-S2 (tibial)
Knee Extension Ankle Dorsiflexion
196-200. Quadriceps L2-L4 203. Tibialis anterior L4-L5 (deep
femoris (all): (femoral) peroneal)
210. Peroneus tertius
196. Rectus femoris L4-S1 (superior L5-S1 (deep
gluteal) 221. Extensor hallucis peroneal)
197. Vastus lateralis longus
L5 (deep peroneal)
198. Vastus 211. Extensor digitorum (L4-S1 also cited)
intermedius longus
L5-S1 (deep
199. Vastus medialis peroneal)
longus
Foot Inversion L4-L5 (tibial)
200. Vastus medialis L4-L5 (deep
oblique 204. Tibialis posterior peroneal)
203. Tibialis anterior L5 (deep peroneal)
185. Tensor fasciae
latae 221. Extensor hallucis L5-S2 (tibial)
longus L5-S2 (tibial)
Knee Internal Rotation (Knee flexed)
222. Flexor hallucis longus
194. Semimembranosus L5-S2 (sciatic 213. Flexor digitorum
[tibial])
longus
193. Semitendinosus L5-S2 (sciatic
[tibial])
195. Sartorius L2-L3 (femoral)
178. Gracilis L2-L3 (obturator) 206. Soleus S1-S2 (tibial)
202. Popliteus L4-S1 (tibial) Foot Eversion
208. Peroneus longus
Knee External Rotation (Knee flexed) L5-S1 (superficial
209. Peroneus brevis peroneal)
192. Biceps femoris: L5-S2 (sciatic
Long head [tibial]) L5-S1 (superficial
peroneal)
4 3 6 Chapter 9 / Ready Reference Anatomy
Part 4. Motions and Their Participating Muscles (Motions of the Neck, Trunk, and Limbs)
205. Gastrocnemius S1-S2 (tibial) 2nd, 3rd, and S2-S3 (lateral
(medial head) 4th, for digits 3, 4, plantar)
L5-S1 (deep and 5
210. Peroneus tertius peroneal)
L5-S1 (deep 220. Plantar interossei:
211. Extensor digitorum peroneal)
longus 1st and 2nd, for S2-S3 (lateral
plantar, deep branch)
digits 3 and 4
3rd, for digit 5 S2-S3 (lateral plantar,
superficial branch)
Motions of the Hallux
219. Dorsal interossei, S2-S3 (lateral
Great Toe Flexion 1st to 4th, for plantar)
digits 2 to 5
Proximal Joint (MP) S1-S2 (medial 214. Flexor digitorum brevis S1-S2 (medial
223. Flexor hallucis brevis plantar) plantar)
222. Flexor hallucis longus L5-S2 (tibial) 213. Flexor digitorum L5-S2 (tibial)
224. Abductor hallucis longus
S1-S2 (medial
225. Adductor hallucis plantar) PIP Joints
S2-S3 (lateral 214. Flexor digitorum brevis S1-S2 (medial
plantar) plantar)
213. Flexor digitorum L5-S2 (tibial)
longus
Distal Joint (IP)
222. Flexor hallucis longus L5-S2 (tibial) DIP Joints
Great Toe Extension (Toe 1) 213. Flexor digitorum L5-S2 (tibial)
longus
Proximal Joint (MP) S1-S3 (lateral
217. Quadratus plantae plantar)
221. Extensor hallucis
longus L5 (deep peroneal) Toe Extension
(L1-S4 also cited)
212. Extensor digitorum Proximal Joints (MP)
brevis L5-S1 (deep
peroneal) 211. Extensor digitorum
longus
Distal Joint (IP) L5-S1 (deep
221. Extensor hallucis longus L5 (deep peroneal) 212. Extensor digitorum peroneal)
brevis
Great Toe Abduction (Away from toe 2) L5-S1 (deep
peroneal)
224. Abductor hallucis S1-S2 (medial Middle and Distal Joints (PIP and DIP)
plantar)
211. Extensor digitorum L5-S1 (deep
Great Toe Adduction (Toward toe 2) longus peroneal)
225. Adductor hallucis S2-S3 (lateral 212. Extensor digitorum L5-S1 (deep
plantar) brevis peroneal)
Motions of Toes 2, 3, and 4 218. Lumbricales: L5-S1 (medial
1st, for digit 2 plantar)
Toe Flexion S2-S3 (lateral
2nd, 3rd, and plantar)
4th, for digits 3, 4,
and 5
MP Joints 220. Plantar interossei for S2-S3 (lateral
digits 3 to 5 plantar)
218. Lumbricales:
1st, for digit 2 L5-S1 (medial 219. Dorsal interossei for S2-S3 (lateral
plantar) digits 2 to 5 plantar)
Chapter 9 / Ready Reference Anatomy 4 3 7
Part 4. Motions and Their Participating Muscles (Motions of the Neck, Trunk, and Limbs)
Toe Abduction (Away from 213. Flexor digitorum L5-S2 (tibial)
axial line through digit 2) longus
L5-S2 (tibial)
219. Dorsal interossei, S2-S3 (lateral DIP Joint S1-S3 (lateral
2nd, 3rd, and plantar) plantar)
4th, for digits 2, 3, 213. Flexor digitorum
and 4 longus
Toe Adduction (Toward axial 217. Quadratus plantae
line through digit 2) (Flexor digitorum
accessorius)
220. Plantar interossei, 1st, S2-S3 (lateral Little Toe Extension
2nd, and 3rd, for plantar)
digits 3, 4, and 5
Motions of the Little Toe Proximal Joint (MP) L5-S1 (deep
peroneal)
211. Extensor digitorum
longus
Little Toe Flexion
Middle and Distal Joints (PIP and DIP)
MP Joint S2-S3 (lateral 211. Extensor digitorum L5-S1 (deep
216. Flexor digiti minimi plantar) longus peroneal)
brevis
S1-S3 (lateral 218. Lumbrical, 4th S2-S3 (lateral
215. Abductor digiti plantar) plantar)
minimi 220. Interosseus, 3rd S2-S3 (lateral
S2-S3 (lateral plantar plantar)
218. Lumbrical, 4th plantar)
Little Toe Abduction (Away
220. Interosseus, 3rd S2-S3 (lateral from digit 4)
plantar plantar)
215. Abductor digiti S1-S3 (lateral
214. Flexor digitorum S1-S2 (medial minimi plantar)
brevis plantar)
213. Flexor digitorum longus L5-S2 (tibial)
PIP Joint Little Toe Adduction (Toward digit 4)
214. Flexor digitorum S1-S2 (medial 220. Interosseus, 3rd S2-S3 (lateral
brevis plantar) plantar plantar)
4 3 8 Chapter 9 / Ready Reference Anatomy