Hypothalamus: Functions Posterior Pituitary

Hormone production & release: Feedback Mechanisms Hypothalamus and Pituitary
-Response to a stimulus has an effect on the original stimulus-

Negative feedback: produces decrease in original stimulus
Positive feedback: produces increase in original stimulus

Hypothalamus: Functions Posterior Pituitary

Sensory signals NEURAL NOT ENDOCRINE
Oxytocin targets:
Hypothalamus uterus- contraction
mammary glands- milk
Behavioral Hormone release from ejection (let-down)
Responses Vasopressin (ADH) targets:
Activity of The Pituitary Gland kidneys- water retention
increase blood volume
Autonomic decrease [Na+]

Nervous System 1

Magnocellular Posterior Pituitary: Pars nervosa
neurosecretory
neurons Herring bodies: dilations of the axon filled with
neurosecretory granules (blue arrows)
Posterior Pituitary Fenestrated capillaries
Infundibulum Pituicytes: astrocyte-like cells , associated with capillaries
(red arrow)

Pars nervosa

http://som.umdnj.edu/histology/lab22/lab22pituitary.html http://medpics.ucsd.edu

Hypothalamic Control of the Anterior Pituitary

Anterior Pituitary is an endocrine gland. Anterior Pituitary
Hormones
Its hormone release controlled by hypothalamic hormones.
Follicle-stimulating hormone*
Release Stimulate Luteinizing hormone *
Thyroid-stimulating hormone *
control or inhibit Adrenocorticotropin *
Growth Hormone
Parvocellular hormones hormone Prolactin
neurosecretory Target cells
release into Target cells *tropic hormones: regulate
cells into 1st 2nd capillary hormone release of target
cells
Hypothalamus capillary bed Anterior bed- portal Throughout
system 2
of Body
infundibulum Pituitary

Anterior Pituitary Parvocellular Anterior Pituitary: Pars Distalis
Neurosecretory
Pars tuberalis Cells Cell Classification based on staining
Pars intermedia characteristics:
Pars distalis
1)! Chromophobes- light staining;
Yellow arrows

2)! Acidophils- bright red staining; Blue
arrows

3)! Basophils- intermediately-stained;
Red arrows

Cell Classification based on functional characteristics: Altered Hypothalamic/Pituitary Hussain Bisad
Function 7feet 9 inches
1)! Somatotropes: 50%, round nuclei, acidophilic, release
growth hormone (somatotropin); +release GHRH and ghrelin, Excessive Growth hormone
- release somatostatin
Giantism/Acromegaly
2)! Lactotropes: 15-20%, large polygonal,oval nuclei, acidophilic
vesicles -when released-chromophobe; prolactin; +THR and Tom Thumb news.bbc.co.uk/.../south_east/6092086.stm?ls
VIP, -dopamine
(2 feet 1 inch)
3)! Corticotropes: 15-20%, medium polygonal, round eccentric & P. T. Barnum
nuclei, basophils, PAS+, produce Adrenocorticotropin
(ACTH), MSH, enkephalin from precursor molecule POMC Insufficient Growth hormone
(proopiomelanocortin); +CRH
Growth Hormone Deficiency
4) Gonadotropes: 10%, small oval w/round eccentric nuclei, Dwarfism
basophil and PAS+, release follicle-stimulating hormone
(FSH) and luteinizing hormone (LH); +GnRH www.pbs.org/.../special_dwarfism_ety.html

5) Tyrotropes: 5%, large, polygonal, basophilia, PAS+, thyroid-
stimulating hormone (TSH), +TRH

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Thyroid Follicular Cells

Thyroid Follicles Arranged around lumen
Epithelium: simple cuboidal or filled with acidophilic
colloid (PAS positive)
low columnar

Follicular Cells
- produce thyroid
hormone
T3 and T4
- spherical nuclei
- basophilic
- microvilli

Parafollicular ( C ) Cells
- produce calcitonin
- follicule periphery
- within basal lamina
- pale staining

Fenestrated capillaries

Parafollicular (C) Cells THYROID: Follicular and Parafollicular cells

Calcitonin: 4

-! Calcitonin secreted in
response to increase in
blood calcium

-! Suppresses osteoclast
function, increase osteiod
calcification

-! Decreases blood calcium
levels

-! Physiological antagonist

to parathyroid hormone

Thyroid Hormone Synthesis

1) Follicular cells produce thyroglobulin and secrete it into
lumen

2)! Follicular cells actively take up iodide and it is oxidized to
iodine and released into the colloid.

3)! Tyrosine residues on thyroglobulin are iodinated to form
MIT and DIT. Mediated by thyroid peroxidase on apical
surface.

MIT= monoiodotyrosine

DIT= diiodotyrosine

thyroid peroxidase

Thyroid Hormone Synthesis Thyroid Hormone Synthesis

4)! MIT + DIT form T3 Still part of thyroglobulin in colloid 5) Upon stimulation with TSH (Thyroid Stimulating
DIT + DIT form T4 Hormone), thyroglobulin is reabsorbed by receptor mediated
endocytosis and combine with lysosomes, releasing T3 and T4.

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Thyroid Hormone Synthesis Thyroid Hormone Targets and Function

Metabolic Activity: T3 >>> T4 - Increases basal metabolic rate (BMR) (heat production)
Amount released from Thyroid: T4 >>> T3 20:1 - Accelerates protein synthesis in children
Transport in blood: Bound to transport (carrier) protein -->
body growth and development
Thyroxine-binding protein brain development
T4 is converted to T3 in kidneys and liver - Enhances sympathetic tone

Thyroid Hormone Targets and Function Thyroid Hormone Release: Negative Feedback

Thyroid Hormone Receptor: intracellular, bound to DNA as Thyroid Releasing Hormone (TRH)
repressor without T3; with T3 present, acts as an activator of Thyroid Stimulating Hormone (TSH)
gene transcription Thyroid Hormones (T3 and T4)

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Diseases of the Thyroid Diseases of the Thyroid

Iodine Deficiency: low T3 + T4, elevated TSH, goiter Hypothyroidism
Hypothyroidism

Diseases of the Thyroid Diseases of the Thyroid

Hyperthyroidism Graves Disease

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Graves Disease: Digestive System
T3 and T4
TSH Alimentary Canal and Associated Organs

Mouth Tongue
Esophagus Teeth
Stomach Salivary Glands
Small Intestine Pancreas
Large Intestine Liver

Gall Bladder

Alimentary Canal Alimentary Canal

Barrier: between internal and external General Structure from Esophagus ---> Anus
environments
Mucosa: Epithelium
Motility: movement of food Lamina Propria
Muscularis Mucosa (smooth muscle)
Secretion: enzymes, mucous, acid,
antibodies Submucosa: Dense irregular connective tissue

Absorption: products of digestion Muscularis externa: Two layers of smooth muscle

Immunological Defense: site of Serosa:simple squamous epithelium, connective tissue
lymphatic tissue

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Barrier- Epithelium Barrier- Epithelium

Oral Cavity: parakeratinized epithelium- most Esophagus: stratified squamous epithelium
superficial cells do not lose nuclei
tongue, gums, hard palate Small and Large Intestine- tight junctions between
columnar cells of simple epithelium
Connective tissue papilla

Immunological Defense Adenoids: lymphatic tissue located high
on the posterior wall of the pharynx.
Tonsils: ring of lymphatic tissue (lymphatic nodules
or follicles) at entrance to respiratory and digestive - similar to tonsils
tracts -! clear antigens from air
- reduced in adults
micro.magnet.fsu.edu/optics/intelplay/gallery... - can be enlarged / inflamed

SYMPTOMS:

-!mouth breathing
-!snoring
-b! ad breath
-c! hronic runny nose
-s! leep apnea
-p! ulmonary hypertension
-!right-sided heart failure

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Immunological Defense Immunological Defense

Gut-associated lymphatic tissue (GALT): diffuse Plasma Cells secrete a special form of antibody,
lymphatic tissue and lymphatic nodules in lamina ==> secreted IgA
propria of small and large intestine
Striking in Appendix and Ileum=> Peyer’s Patches -Dimeric
-Linked via J chain and
MALT=Mucous associated lymphatic Tissue secretory component
-More stable
-More resistant to
enzymatic digestion
-in saliva, milk, and
mucous membranes of
respiratory and
digestive tracts

Possible modes of defense Immunological Defense
mediated by IgA binding to its
receptor, pIgR, (the secretory Peyer’s Patches
component , SC). Lymph nodules
capped by
(a)! pIgR-driven export of specialized
dimeric IgA with J chain epithelial cells,
(IgA+J) =>M Cells

(b)! Neutralization of infecting www.bu.edu/histology/p/12001oba.htm
virus and transport of viral
products from the lumen. 10

(c)! Intracellular neutralization
of endotoxin (LPS) from
Gram-negative bacteria.

(d)! Clearance of antigen (Ag)
that has breached the
mucosal barrier.

From Trends Immunol. 2004, 25:150-57.

M Cells M Cells

- Follicle-Associated -! have extensive inpocketings of basal membrane containing
Epithelium (FAE): epithelial T and B lymphocytes
cells associated with lymph
nodules of MALT www.rcai.riken.go.jp/eng/group/epi/

-! look for absence of
goblet cells over Peyer’s
Patch

-! apical surface microfolds
rather than microvilli

- connected to neighbors
with tight junctions

M Cells: specialized for transepithelial Motility

transport: deliver intact foreign antigens and Muscularis Mucosa: 2 layers of smooth muscle
microorganisms from lumen to immune cells inner-circular, outer-longitudinal
responsible for moving the mucosa

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Motility Motility: Muscularis Externa

Muscularis Externa: mixes, propels contents of lumen

2 thick layers of smooth muscle

inner layer=> circularly-oriented layer
-tight spiral

outer layer=>longitudinally-oriented layer
-loose spiral

Between muscle layers- Nervous innervation

Myenteric plexis (Auerbach’s plexis)

Motility: Muscularis Externa Motility

MUSCULARIS EXTERNA EXCEPTIONS:
Striated muscle in proximal esophagus (upper 1/3) and anus

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MUSCULARIS EXTERNA EXCEPTIONS: Secretion

Teniae Coli: 3 thickened bands of longitudinal layer -! carried out by epithelial cells and associated glands
large intestine- -! secretions include:

Antibodies: IgA
Lubrication substances
Aid for digestion: hydrochloric acid & enzymes
Hormones
Water
-!secretions from salivary glands, stomach, small and
large intestine

Anatomy of the Stomach Anatomy of the Stomach

3 regions: 3 regions:
Cardiac Cardiac
Pyloric Pyloric
Fundic Fundic

Rugae: longitudinal folds or ridges on inner surface Rugae: longitudinal folds or ridges on inner surface
Simple columnar epithelium

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Each stomach region Anatomy of the Small Intestine
has distinctive glands.
3 components: Duodenum, Jeunum, Ileum
•!Cardiac glands - Plicae circularis
•P! yloric glands - Villi
•!Fundic glands - Microvilli

-gastric pits - Simple columnar epithelium
-isthmus

cell replication

-neck
-base or fundus

Anatomy of the Small Intestine

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