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Short notes on Structure of liver for 5 marks

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liver structure anatomy lobule portal triad

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liver lobule histology hepatocytes

This educational image combines a schematic diagram (A) and a light microscopy photograph (B) illustrating human liver microanatomy. Part A is an anatomical diagram of a typical hepatic lobule, demonstrating its hexagonal structure. Key labeled components include the central vein at the lobule's core and the portal triad at the vertices, which consists of a hepatic artery, portal vein, and bile duct. It shows hepatocytes arranged in cords radiating toward the central vein, interspersed with sinusoids that facilitate fluid transport. Part B is a diagnostic histology image of human liver tissue stained with hematoxylin and eosin (H&E). The parenchyma is visible as a dense arrangement of pink-stained hepatic cords and clear, white-appearing sinusoids. Several central veins are marked with asterisks (*). The image provides a side-by-side comparison between the idealized anatomical model and actual clinical histology, suitable for medical students learning hepatology and tissue architecture.

This educational image combines a schematic diagram (A) and a light microscopy photograph (B) illustrating human liver microanatomy. Part A is an anatomical diagram of a typical hepatic lobule, demonstrating its hexagonal structure. Key labeled components include the central vein at the lobule's core and the portal triad at the vertices, which consists of a hepatic artery, portal vein, and bile duct. It shows hepatocytes arranged in cords radiating toward the central vein, interspersed with sinusoids that facilitate fluid transport. Part B is a diagnostic histology image of human liver tissue stained with hematoxylin and eosin (H&E). The parenchyma is visible as a dense arrangement of pink-stained hepatic cords and clear, white-appearing sinusoids. Several central veins are marked with asterisks (*). The image provides a side-by-side comparison between the idealized anatomical model and actual clinical histology, suitable for medical students learning hepatology and tissue architecture.

Brightfield light microscopy of a liver biopsy stained with hematoxylin and eosin (H&E). The specimen shows hepatic parenchyma with cords of polygonal hepatocytes separated by sinusoidal capillaries and occasional central veins. The overall lobular architecture appears preserved, with uniform cytoplasmic eosinophilia and round, centrally located nuclei. Portal tracts are not clearly delineated within this low magnification field, but no marked interface activity or interface hepatitis is visible. There is no appreciable steatosis, hepatocellular ballooning, necrosis, or inflammatory infiltrate evident at this magnification. Fibrous septa or cirrhotic nodules are not observed. The tissue appears well preserved with minimal artifact from sectioning. Overall, the histology is compatible with benign hepatic parenchyma in a non-diseased state at this plane of view. This image serves as a reference for normal hepatic architecture and cellular morphology, useful in educational comparisons with diseased liver specimens. Potential clinical applications include baseline histology evaluation, quality control in biopsy processing, and teaching scenarios illustrating hepatocyte cords, sinusoidal arrangement, central veins, and portal areas. Relevant keywords: liver biopsy, hepatic lobule, hepatocytes, sinusoids, central vein, portal tract, H&E, brightfield, normal liver.

Brightfield light microscopy of a liver biopsy stained with hematoxylin and eosin (H&E). The specimen shows hepatic parenchyma with cords of polygonal hepatocytes separated by sinusoidal capillaries and occasional central veins. The overall lobular architecture appears preserved, with uniform cytoplasmic eosinophilia and round, centrally located nuclei. Portal tracts are not clearly delineated within this low magnification field, but no marked interface activity or interface hepatitis is visible. There is no appreciable steatosis, hepatocellular ballooning, necrosis, or inflammatory infiltrate evident at this magnification. Fibrous septa or cirrhotic nodules are not observed. The tissue appears well preserved with minimal artifact from sectioning. Overall, the histology is compatible with benign hepatic parenchyma in a non-diseased state at this plane of view. This image serves as a reference for normal hepatic architecture and cellular morphology, useful in educational comparisons with diseased liver specimens. Potential clinical applications include baseline histology evaluation, quality control in biopsy processing, and teaching scenarios illustrating hepatocyte cords, sinusoidal arrangement, central veins, and portal areas. Relevant keywords: liver biopsy, hepatic lobule, hepatocytes, sinusoids, central vein, portal tract, H&E, brightfield, normal liver.

Imaging modality: Light microscopy of a Hematoxylin and Eosin (H&E) stained liver biopsy section examined under brightfield illumination. Primary site: liver parenchyma, hepatic lobule, hepatocytes arranged in cords separated by sinusoids. The cellular morphology shows polygonal hepatocytes with abundant eosinophilic granular cytoplasm and centrally placed round nuclei, occasional binucleation, and well-preserved cytoplasmic borders. Sinusoidal spaces appear patent with mild vascular congestion; there is no conspicuous steatosis, confluent necrosis, or prominent apoptosis in this field. Intercellular boundaries are intact; there is no significant inflammatory infiltrate or fibrotic septa evident in this limited view. Overall architecture is consistent with normal hepatic parenchyma, though a small sampling may miss portal tracts or fibrotic changes. No overt cytologic atypia or neoplastic features are obvious in this image. Diagnostic relevance: this image documents typical hepatocellular morphology suitable for educational reference and for distinguishing normal liver histology from inflammatory, degenerative, or neoplastic processes in hepatology and pathology practice. Potential clinical applications include baseline histology assessment in liver biopsies, evaluation of suspected fatty liver disease, viral hepatitis, or hepatocellular carcinoma if cytologic atypia present. Educational relevance extends to medical students, residents, and fellows; helps practice pattern recognition, differential diagnosis, and correlation with serology, imaging, and clinical course.

Imaging modality: Light microscopy of a Hematoxylin and Eosin (H&E) stained liver biopsy section examined under brightfield illumination. Primary site: liver parenchyma, hepatic lobule, hepatocytes arranged in cords separated by sinusoids. The cellular morphology shows polygonal hepatocytes with abundant eosinophilic granular cytoplasm and centrally placed round nuclei, occasional binucleation, and well-preserved cytoplasmic borders. Sinusoidal spaces appear patent with mild vascular congestion; there is no conspicuous steatosis, confluent necrosis, or prominent apoptosis in this field. Intercellular boundaries are intact; there is no significant inflammatory infiltrate or fibrotic septa evident in this limited view. Overall architecture is consistent with normal hepatic parenchyma, though a small sampling may miss portal tracts or fibrotic changes. No overt cytologic atypia or neoplastic features are obvious in this image. Diagnostic relevance: this image documents typical hepatocellular morphology suitable for educational reference and for distinguishing normal liver histology from inflammatory, degenerative, or neoplastic processes in hepatology and pathology practice. Potential clinical applications include baseline histology assessment in liver biopsies, evaluation of suspected fatty liver disease, viral hepatitis, or hepatocellular carcinoma if cytologic atypia present. Educational relevance extends to medical students, residents, and fellows; helps practice pattern recognition, differential diagnosis, and correlation with serology, imaging, and clinical course.

This is a light-field histopathology image of a liver biopsy section stained with Hematoxylin and Eosin (H&E). The image presents a low-magnification overview of hepatic parenchyma, showing cords of polygonal hepatocytes arranged in plates separated by sinusoidal spaces. The lobular architecture is visible, with a dense pink cytoplasmic matrix and basophilic nuclei; there is uniform cellular density without obvious necrosis, conspicuous inflammatory infiltrate, or confluent fibrotic bands at this field of view. The portal tracts are not clearly delineated in this orientation, and bile ducts or arterial branches are not readily identified. Overall liver architecture appears preserved, consistent with non-specific or normal hepatic tissue in this field. This image is suitable as an educational reference for basic liver histology, including identification of hepatocytes, sinusoids, and the hepatic lobule. Potential clinical uses include teaching hepatology and pathology, cross-reference for normal hepatic histology, and comparison against fatty change, steatosis, hepatitis, fibrosis, or cirrhosis in broader sampling. The image may be used to illustrate histological features of normal hepatic parenchyma, guide differential diagnosis when pathology is present, and enhance radiology-pathology correlation exercises in medical education. This description emphasizes reliable terminology for search indexing and clinical education.

This is a light-field histopathology image of a liver biopsy section stained with Hematoxylin and Eosin (H&E). The image presents a low-magnification overview of hepatic parenchyma, showing cords of polygonal hepatocytes arranged in plates separated by sinusoidal spaces. The lobular architecture is visible, with a dense pink cytoplasmic matrix and basophilic nuclei; there is uniform cellular density without obvious necrosis, conspicuous inflammatory infiltrate, or confluent fibrotic bands at this field of view. The portal tracts are not clearly delineated in this orientation, and bile ducts or arterial branches are not readily identified. Overall liver architecture appears preserved, consistent with non-specific or normal hepatic tissue in this field. This image is suitable as an educational reference for basic liver histology, including identification of hepatocytes, sinusoids, and the hepatic lobule. Potential clinical uses include teaching hepatology and pathology, cross-reference for normal hepatic histology, and comparison against fatty change, steatosis, hepatitis, fibrosis, or cirrhosis in broader sampling. The image may be used to illustrate histological features of normal hepatic parenchyma, guide differential diagnosis when pathology is present, and enhance radiology-pathology correlation exercises in medical education. This description emphasizes reliable terminology for search indexing and clinical education.

I have excellent content from both the Histology textbook and Guyton's Physiology, plus diagrams. Here is the complete 5-mark short note:

Structure of the Liver

General Features

The liver is the largest gland in the body, weighing approximately 1.5 kg (about 2% of body weight). It is located in the right hypochondrium under the diaphragm. It contains 50,000-100,000 lobules as its functional units.
  • Guyton and Hall Textbook of Medical Physiology

Structural Components

The liver is composed of four main components:
  1. Parenchyma - plates of hepatocytes
  2. Connective tissue stroma
  3. Sinusoidal capillaries (hepatic sinusoids)
  4. Perisinusoidal spaces (Space of Disse)

Functional Units of the Liver

There are three models to describe the liver's functional unit:
UnitShapeDescription
Classic LobulePolygonal/hexagonalHepatocyte plates radiate from a central vein; portal triads at corners
Portal LobuleTriangularEmphasizes bile secretion; portal tract at centre
Liver AcinusDiamond-shapedBest correlates with blood perfusion, metabolic activity, and pathology; divided into Zones 1, 2, 3

Classic Lobule - Key Details

  • Hepatocytes form irregular anastomosing plates radiating toward a central vein
  • At each corner of the hexagon lies the portal triad, which contains:
    • Branch of the portal vein
    • Branch of the hepatic artery
    • Bile duct
    • Small lymphatic vessels
  • The central vein drains into hepatic veins and then the inferior vena cava

Hepatic Sinusoids

  • Irregular vascular channels running between hepatocyte plates
  • Receive mixed blood: 75% from portal vein (venous) + 25% from hepatic artery (arterial)
  • Total hepatic blood flow ~ 1,350 mL/min (27% of cardiac output)
  • Lined by thin, discontinuous (fenestrated) endothelium

Space of Disse (Perisinusoidal Space)

  • Narrow space between the sinusoidal endothelium and hepatocytes
  • Site of exchange of materials between blood and hepatocytes
  • Large pores in endothelium allow free diffusion of plasma proteins into this space
  • Connects with lymphatic vessels in interlobular septa - excess fluid drains as lymph

Special Cell Types in Sinusoids

CellLocationFunction
Kupffer cells (sinusoidal macrophages)Line sinusoidal wallPhagocytose bacteria, worn-out RBCs; recycle iron
Hepatic stellate cells (Ito cells)Perisinusoidal spaceStore Vitamin A in lipid droplets; become myofibroblasts in pathology (fibrosis)

Hepatocytes

  • Constitute 80% of liver cells
  • Large, polygonal cells with spherical nuclei (often binucleated)
  • Acidophilic cytoplasm with abundant sER, rER, mitochondria, peroxisomes, and Golgi complexes
  • Basal surface: faces Space of Disse (exchange)
  • Apical surface: forms bile canaliculi with adjacent hepatocyte

Bile Drainage Pathway

Hepatocyte → Bile canaliculi → Canals of Hering → Intrahepatic bile ductules → Interlobular bile ducts (portal triad) → Left & Right hepatic ducts → Common hepatic duct → Gallbladder / Duodenum
  • Canals of Hering harbor hepatic stem cells
  • Biliary tree is lined by cholangiocytes (cuboidal/columnar epithelium)

Diagram: Liver Lobule and Histology

Hepatic lobule diagram and H&E histology
The diagram (A) shows the hexagonal classic lobule with central vein, portal triads at vertices, and sinusoids. (B) is H&E histology showing hepatocyte cords and sinusoids.
Sources: Histology: A Text and Atlas (7e), p. 1733 | Guyton and Hall Textbook of Medical Physiology

Short notes on Tongue for 5 marks

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tongue anatomy papillae taste buds diagram

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I now have all the content needed - excellent diagrams and comprehensive textbook data. Here is the complete 5-mark short note:

Structure of the Tongue

Definition & General Features

The tongue is a muscular organ that projects into the oral cavity from its inferior surface. It is covered by mucosa and plays roles in mastication, swallowing, speech, and taste. It is divided into left and right halves by a median sagittal fibrous septum.

Surfaces and Parts

Tongue anatomy - sagittal section and dorsal surface with papillae
The tongue has two surfaces and two parts:
FeatureDescription
Dorsal (superior) surfaceAnterior 2/3 bears papillae; posterior 1/3 has lingual tonsils
Inferior surfaceNo papillae; has the frenulum (median fold) and lingual veins
Oral part (anterior 2/3)Lies in the oral cavity; horizontal plane
Pharyngeal part (posterior 1/3)Forms anterior wall of oropharynx; vertical plane
  • The two parts are separated by a V-shaped groove - the sulcus terminalis
  • At the apex of the V is the foramen cecum - embryological remnant marking the origin of the thyroid gland (thyroglossal duct invagination)
  • The root of the tongue is attached to the mandible and hyoid bone

Muscles of the Tongue

Lingual muscles are of two types:

Intrinsic Muscles (confined to the tongue, no external attachment)

Run in three planes - unique to the tongue, allowing great flexibility:
MuscleFunction
Superior longitudinalShortens tongue; curls apex upward
Inferior longitudinalShortens tongue; turns apex downward
TransverseNarrows and elongates tongue
VerticalFlattens and widens tongue

Extrinsic Muscles (one attachment outside the tongue)

MuscleOriginAction
GenioglossusMental spine of mandibleProtrudes tongue (main protruder)
HyoglossusHyoid boneDepresses tongue
StyloglossusStyloid processRetracts and elevates tongue
PalatoglossusPalatine aponeurosisElevates posterior tongue
All muscles innervated by CN XII (Hypoglossal nerve) except palatoglossus (innervated by CN X - Vagus via pharyngeal plexus).

Papillae of the Tongue (Dorsal surface - Anterior 2/3)

Tongue dorsal surface showing all papillae types and taste bud structure
There are four types of lingual papillae:
TypeShapeLocationTaste BudsKey Feature
FiliformCone/thread-shaped, pointedAll over anterior dorsumNoneMost numerous; heavily keratinized; provide friction for food movement
FungiformMushroom/bulbous-shapedScattered across dorsal surface, concentrated at marginsPresentWell-vascularized lamina propria core; lightly keratinized
FoliateLeaf-like folds/ridgesLateral sides of tonguePresentRudimentary in adults; best developed in children
Vallate (Circumvallate)Large, blunt cylinders with surrounding trenchV-shaped row just anterior to sulcus terminalisMost abundant (in trench walls)Only 8-12 in number; largest papillae; serous (von Ebner's) glands open into trench
All papillae except filiform bear taste buds and are called gustatory papillae.

Taste Buds

  • Oval structures embedded in the epithelium of papillae
  • Contain three cell types:
    1. Gustatory (taste) cells - bear microvilli projecting through the taste pore
    2. Supporting cells - unclear function
    3. Basal stem cells - replace worn gustatory cells
  • Taste is detected when dissolved chemicals contact microvilli at the taste pore

Posterior Third (Pharyngeal Surface)

  • No papillae
  • Contains lingual tonsil - nodules of lymphoid tissue in the submucosa giving it an irregular, bumpy appearance

Nerve Supply Summary

FunctionAreaNerve
General sensation (touch, pain, temp)Anterior 2/3Lingual nerve (CN V3 - Mandibular)
TasteAnterior 2/3Chorda tympani (CN VII - Facial)
General sensation + TastePosterior 1/3Glossopharyngeal nerve (CN IX)
General sensationRoot/epiglottisVagus nerve (CN X)
All musclesBoth partsHypoglossal nerve (CN XII)
Sources: Gray's Anatomy for Students (4e) | Junqueira's Basic Histology (17e), p. 738-739 | Histology: A Text and Atlas (7e), p. 1419-1421

Essay on pitiatry hormone for 10 marks question

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pituitary gland anterior posterior hormones diagram

This pathophysiology diagram illustrates the role of vasopressin (AVP) in the regulation of the Hypothalamic-Pituitary-Adrenal (HPA) axis and renal water retention. A sagittal brain illustration highlights the Paraventricular Nucleus (PVN), which is subdivided into parvocellular (pPVN) and magnocellular (mPVN) regions. The pPVN releases both AVP and Corticotropin-Releasing Hormone (CRH) into the anterior pituitary (AP). Within the AP, these hormones bind to V1bR and CRHR1 receptors, respectively, on proopiomelanocortin (POMC) cells to stimulate the release of Adrenocorticotropic Hormone (ACTH). ACTH subsequently acts on the adrenal gland to stimulate glucocorticoid production, mediating the systemic stress response. Simultaneously, the mPVN produces AVP, which is transported through the posterior pituitary (PP) into the bloodstream to act on the kidney, promoting water retention. The diagram effectively maps the dual neuroendocrine pathways of AVP, linking hypothalamic activity to endocrine stress responses and physiological osmoregulation. Key labels include ACTH, pPVN, mPVN, V1bR, CRHR1, and POMC.

This pathophysiology diagram illustrates the role of vasopressin (AVP) in the regulation of the Hypothalamic-Pituitary-Adrenal (HPA) axis and renal water retention. A sagittal brain illustration highlights the Paraventricular Nucleus (PVN), which is subdivided into parvocellular (pPVN) and magnocellular (mPVN) regions. The pPVN releases both AVP and Corticotropin-Releasing Hormone (CRH) into the anterior pituitary (AP). Within the AP, these hormones bind to V1bR and CRHR1 receptors, respectively, on proopiomelanocortin (POMC) cells to stimulate the release of Adrenocorticotropic Hormone (ACTH). ACTH subsequently acts on the adrenal gland to stimulate glucocorticoid production, mediating the systemic stress response. Simultaneously, the mPVN produces AVP, which is transported through the posterior pituitary (PP) into the bloodstream to act on the kidney, promoting water retention. The diagram effectively maps the dual neuroendocrine pathways of AVP, linking hypothalamic activity to endocrine stress responses and physiological osmoregulation. Key labels include ACTH, pPVN, mPVN, V1bR, CRHR1, and POMC.

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I now have comprehensive content from Ganong's, Guyton's, and Robbins' for a full 10-mark essay. Let me compose the complete answer.

Pituitary Hormones - Essay (10 Marks)

Introduction

The pituitary gland (hypophysis) is a small, bean-shaped gland lying at the base of the brain within the sella turcica of the sphenoid bone. It is connected to the hypothalamus by the pituitary stalk (infundibulum). Often called the "master gland" of the endocrine system, the pituitary regulates most other endocrine glands through its trophic hormones.
It is composed of two morphologically and functionally distinct parts:
  • Anterior lobe (Adenohypophysis) - ~80% of the gland
  • Posterior lobe (Neurohypophysis) - ~20% of the gland

PART I: ANTERIOR PITUITARY (ADENOHYPOPHYSIS)

Cell Types of the Anterior Pituitary

Histologically, the anterior pituitary contains cells with acidophilic, basophilic, or chromophobic cytoplasm. There are six terminally differentiated cell types, each producing specific hormones:
Cell TypeHormone ProducedStaining
SomatotrophsGrowth Hormone (GH)Acidophil
MammosomatotrophsGH + ProlactinAcidophil
LactotrophsProlactin (PRL)Acidophil
CorticotrophsACTHBasophil
ThyrotrophsTSHBasophil
GonadotrophsFSH + LHBasophil

Hormones of the Anterior Pituitary

The anterior pituitary secretes six major hormones:
Anterior pituitary hormones and their target organs

1. Growth Hormone (GH) / Somatotropin

  • Chemical nature: Protein (191 amino acids)
  • Actions:
    • Stimulates linear bone growth via somatomedins (IGF-1, produced by liver)
    • Promotes protein synthesis (anabolic effect)
    • Anti-insulin / diabetogenic - raises blood glucose
    • Promotes lipolysis (fat mobilization)
    • Stimulates uptake of amino acids into cells
  • Regulation:
    • Stimulated by: GHRH (Growth Hormone-Releasing Hormone)
    • Inhibited by: Somatostatin (GIH)
  • Excess: Gigantism (before epiphyseal fusion), Acromegaly (after fusion)
  • Deficiency: Dwarfism (pituitary dwarfism)

2. Thyroid-Stimulating Hormone (TSH) / Thyrotropin

  • Chemical nature: Glycoprotein (alpha + beta subunits)
  • Actions:
    • Stimulates synthesis and release of T3 and T4 from thyroid gland
    • Promotes thyroid gland growth (hypertrophy and hyperplasia)
  • Regulation:
    • Stimulated by: TRH (Thyrotropin-Releasing Hormone)
    • Inhibited by: T3/T4 (negative feedback), somatostatin

3. Adrenocorticotropic Hormone (ACTH) / Corticotropin

  • Chemical nature: Polypeptide (39 amino acids); derived from pro-opiomelanocortin (POMC)
  • Actions:
    • Stimulates synthesis and secretion of glucocorticoids (cortisol) and sex steroids from adrenal cortex
    • Mild stimulation of mineralocorticoid (aldosterone) secretion
    • Has melanocyte-stimulating activity (shares sequence with MSH)
  • Regulation:
    • Stimulated by: CRH (Corticotropin-Releasing Hormone), stress, low cortisol
    • Inhibited by: cortisol (negative feedback)
  • Excess: Cushing's disease

4. Follicle-Stimulating Hormone (FSH)

  • Chemical nature: Glycoprotein
  • Actions (Females): Stimulates growth of ovarian follicles and estrogen secretion
  • Actions (Males): Stimulates spermatogenesis and Sertoli cells
  • Regulation: Stimulated by GnRH; inhibited by inhibin (from gonads)

5. Luteinizing Hormone (LH)

  • Chemical nature: Glycoprotein
  • Actions (Females): Triggers ovulation, formation of corpus luteum, secretion of progesterone
  • Actions (Males): Stimulates Leydig cells of testes → testosterone production (hence called ICSH - Interstitial Cell-Stimulating Hormone in males)
  • Regulation: Stimulated by GnRH; inhibited by sex steroids

6. Prolactin (PRL)

  • Chemical nature: Protein (198 amino acids)
  • Actions:
    • Stimulates breast development and lactation (milk production)
    • Inhibits GnRH secretion → suppresses ovulation during breastfeeding
  • Regulation: Unique - predominantly under inhibitory control
    • Inhibited by: Dopamine (PIH - Prolactin Inhibiting Hormone) from hypothalamus
    • Stimulated by: TRH, VIP, suckling reflex
  • Excess (Hyperprolactinemia): Galactorrhea, amenorrhea, infertility

PART II: POSTERIOR PITUITARY (NEUROHYPOPHYSIS)

The posterior pituitary does not synthesize hormones; it merely stores and releases them. Hormones are synthesized in the hypothalamic nuclei and transported via axons:
HormoneSynthesized inTransported by
ADH (Vasopressin)Primarily supraoptic nucleusNeurophysin II
OxytocinPrimarily paraventricular nucleusNeurophysin I
The pituicytes (glial-like support cells) of the posterior pituitary serve only as a structural framework.

7. Antidiuretic Hormone (ADH) / Vasopressin

  • Chemical nature: Nonapeptide (9 amino acids): Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-GlyNH₂
  • Actions:
    • Increases water reabsorption in collecting ducts of kidneys (via V2 receptors - inserts aquaporin-2 channels)
    • At high doses: vasoconstriction (via V1 receptors) → raises blood pressure
    • Antidiuresis - concentrates urine
  • Stimuli for release:
    • Increased plasma osmolality (most potent)
    • Decreased blood volume/pressure
    • Stress, nausea, nicotine
  • Deficiency: Diabetes Insipidus (massive dilute urine output)
  • Excess: SIADH (Syndrome of Inappropriate ADH secretion) → hyponatremia

8. Oxytocin

  • Chemical nature: Nonapeptide (9 amino acids): Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-GlyNH₂ (differs from ADH in positions 3 and 8)
  • Actions:
    • Stimulates uterine contractions during labor (used clinically to induce labor)
    • Stimulates milk ejection (let-down reflex) from breast - acts on myoepithelial cells
    • Plays a role in social bonding and maternal behavior
  • Stimuli for release:
    • Stretching of the cervix during labor (Ferguson reflex)
    • Suckling of the nipple
  • Clinical use: Synthetic oxytocin (Pitocin) used to induce/augment labor and reduce postpartum hemorrhage

Hypothalamic Control Summary

Anterior pituitary secretion is controlled by hypophysiotropic hormones carried from the hypothalamus via the hypothalamo-hypophyseal portal venous plexus:
Hypothalamic HormoneEffect on Anterior Pituitary
CRH↑ ACTH
TRH↑ TSH, ↑ Prolactin
GHRH↑ GH
Somatostatin (GIH)↓ GH, ↓ TSH
GnRH↑ FSH, ↑ LH
Dopamine (PIH)↓ Prolactin

Summary Table: All Pituitary Hormones

LobeHormoneChemical NatureTargetMain Action
AnteriorGHProteinLiver, boneGrowth, anabolism
AnteriorTSHGlycoproteinThyroidT3/T4 secretion
AnteriorACTHPolypeptideAdrenal cortexCortisol secretion
AnteriorFSHGlycoproteinGonadsFollicle growth/spermatogenesis
AnteriorLHGlycoproteinGonadsOvulation/testosterone
AnteriorProlactinProteinBreastLactation
PosteriorADHNonapeptideKidneysWater retention
PosteriorOxytocinNonapeptideUterus/breastLabor/milk ejection
Sources: Ganong's Review of Medical Physiology (26e) | Guyton and Hall Textbook of Medical Physiology | Robbins, Cotran & Kumar Pathologic Basis of Disease
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