This document summarizes the gross anatomy, histology, development and functional connections of the pituitary gland. It notes that the pituitary gland is divided into the anterior and posterior lobes. The anterior lobe develops from Rathke's pouch and produces several important hormones. The posterior lobe develops from the infundibulum and stores and releases oxytocin and vasopressin. The pituitary gland is connected to the hypothalamus via the hypothalamic-hypophyseal portal system and tract, allowing it to regulate hormone production. Common pituitary tumors and their effects are also briefly discussed.

1. Gross Anatomy & Histology of Pituitary Gland
including Development
Dr. Prabhakar Yadav
Assistant Professor
Department of Human Anatomy
B.P. Koirala Institute of Health Sciences

2. Adenohypophysis (anterior pituitary) ; Neurohypophysis(posterior pituitary).
Adenohypophysis:
formed by Rathke pouch(3rd wk) -
ectodermal derived evagination from roof
of the oral cavity
Rathke pouch-
Looses connection to pharynx (By 2nd mth),
forms epithelial vesicle and grows around
infundibular stalk

3. Infundibulum is downgrowth (evagination) of neurectoderm of hypothalamus/floor of the thirdventricle /floor of
diencephalon just posterior to the optic chiasm
Infundibulum grows and expands distally forming pars posterior (posterior lobe/pars nervosa), while infundibulum
remain attached to floor of hypothalamus.
Neurohypophysis: formed by infundibulum

4. •Anterior wall of vesicle grows extensively to form pars anterior
•Posterior wall grows only a little and fuses into pars posterior, forming pars intermedia
•Cells of pars anterior grows around infundibular stalk- forming pars tuberalis
•Remnant of vesicular lumen forms intraglandular cleft separating pars anterior and pars intermedia

5. With formation of definitive oral cavity & pharynx, the original site of
attachment of Rathke’s pouch comes to lie in roof of nasopharynx.
Tract of Rathke’s pouch forms craniopharyngeal canal.
Remnant of craniopharyngeal canal may gives rise tumors called
craniopharyngiomas -seen in relation to sphenoid bone forming roof of
nasopharynx.

6. Hypophysis Cerebri(Pituitary gland):
Situated: in base of brain

7. Lies in-
hypophyseal fossa / sella turcica /
pituitary fossa
Fossa – roofed by diaphragma sellae-
fold of dura mater, covers pituitary
gland & has an opening for passage
of infundibulum connecting the gland
to hypothalamus.
Shape – oval
anteroposteriorly- 8mm
transversely – 12 mm

8. Relation
Superiorly:
1. diaphragma sellae
2. Optic chiasma
3. Tuber cinerium
4. Infundibular recess of 3rd
ventricle
Inferiorly:
1. venous channels between
two layers of dura mater
2. Hypophyseal fossa
3. Sphenoidal air sinuses
On each side: Cavernous sinuses with its contents

9. Adenohypophysis:
Anterior lobe/ Pars anterior / Pars distalis /
Pars glandularis – largest part
Intermediate lobe/ pars intermedia :
Thin strip separated from anterior lobe by
intraglandular cleft (remnant of--- )
Tuberal lobe or pars tuberalis:
upward extension of anterior lobe that surrounds &
forms part of infundibulum
Neurohypophysis :
Posterior lobe or neural lobe / pars posterior/ pars
nervosa: smaller , lies in posterior concavity of large
anterior lobe
Infundibular stem: contains neural connections of
posteriror lobe with hypothalamus
Mediann eminence of tuber cinerium: continuous
with infundibular stem

10. Arterial Supply:
1. Superior hyophyseal artery
Supplies: (a)Ventral part of hypothalamus
(b) upper part of infundibulum &
(c) Lower part of the infundibulum via
Trabecular artery.
2.Inferor hypophyseal artery:
• Divides into--- medial & lateral branches
Joins to form arterial ring around posterior lobe.
Branches of arterial ring supplies:
(a) posterior lobe &
(b) Anastomose with branches from superior
hypophyseal artery.

11. Pars distalis- supplied exclusively by portal vessels arising
from capillary tufts formed by the superior hypophyseal
arteries
Long portal vessels drains: (a) median eminence
(b) upper infundibulum,
short portal vessels drains: (a)Lower infundibulum.
Portal vessels : carry hormone releasing factors
from the hypothalamus to anterior lobe where
they control the secretory cycles of different glandular
cells.

12. Venous Drainage:
• Short (hypophyseal) veins emerge on surface of gland
• Drain into neighbouring dural venous sinuses.
• hormones are carried to their target cells through
venous blood

13. Functional Connections with Hypothalamus:
Hypothalamohypophysial Tract
Consists of:
Nerve fibres arising from supraoptic &
paraventricular nuclei of hypothalamus and
projecting into posterior lobe of pituitary gland.
Vasopressin( ADH) & Oxytocin produced in
supraoptic & paraventricular nuclei are
transported by nerve fibres of the tract & stored
in nerve terminals (Herring bodies) of these
fibres in neurohypophysis.
Hormones are released in venous sinusoids as
and when necessary.

14. Hypothalamohypophysial Portal System:
Two sets of capillaries:
• One in the hypothalamus (median eminence)
• Other in hypophysis cerebri (sinusoids of pars anterior).
Neurons of the hypothalamus produce hormones-releasing
factors in the capillaries of median eminence & upper part
of infundibulum.
These are carried by the portal system to pars anterior
where they stimulate it to release appropriate hormones.

15. Pituitary tumors:
commonest tumor -pituitary adenoma
Produces 2 types of symptoms:
Symptoms due to pressure adjacent structures :
• Enlargement of hypophyseal fossa: intrasellar growth
of an adenoma.
• Bitemporal hemianopia
• Ophthalmoplegia :pressure on cavernous sinus.
Symptoms due to endocrine disturbances:
• Gigantism before puberty and acromegaly in adults:
excessive secretion of growth (GH) hormone.
• Dwarfism: hyposecretion of GH in infants & children.
•
• Cushing syndrome: Excessive secretion ACTH.
• Diabetes insipidus: involvement of posterior lobe.
Decreased secreation of ADH – due to distruction of
neurohypophysis due to surgery, radiation, head injury,
inflammatory & neoplastic lesion of the hypothalamo-
hypophyseal axis.
Feature: Excreation of large volume of dilute urine of
specific gravity less than 1.01, polyuria & polydipsia.

16. Histology:

17. Pars Anterior:
Pars Anterior:
cords of cells -responsible for production of different hormones -
separated by fenestrated sinusoids.
Chromophil cells (50%)- have brightly staining granules.
acidophil (alpha cells (43%)),-granules stain with acid dyes
basophil (beta cells) (7%)- granules stain with basic dyes.
chromophobe cells (50%) - granules are not prominent.

18. Acidophil Cells
(1) Somatotrophs produce: somatotropin [STH], or
growth hormone [GH]).
(2) Mammotrophs (or lactotrophs)produce:
Mammotropic hormone (mammotropin, prolactin (PRL)
Lactogenic hormone (LTH)
Basophil Cells
1) corticotrophs produce: corticotropic hormone (ACTH).
2) Thyrotrophs produce: thyrotropic hormone ( TSH)
3) Gonadotrophs (delta basophils) )(10% ) produce: two hormones
Follicle stimulating hormone (FSH):
stimulates growth of ovarian follicles
stimulates secretion of oestrogens by the ovaries
Stimulates spermatogenesis.
Luteinizing hormone (LH): stimulates maturation of corpus luteum &
secretion of progesterone
stimulates production of androgens by interstitial cells of the testes
interstitial cell stimulating hormone (ICSH)

19. Chromophobe Cells:
Immunocytochemistry shows that they represent cells
similar to the various types of chromophils including
mammotrophs, somatotrophs, thyrotrophs, gonadotrophs
or corticotrophs.
Pars Tuberalis:
-consists of undifferentiated cells.
- acidophil & basophil cells are also present.
Pars Intermedia: poorly developed
conspicuous feature--presence of colloid filled vesicles.
-----Vesicles are remnants of pouch of Rathke.
Some cells of pars intermedia produce:
• Melanocyte stimulating hormone (MSH).
• ACTH
• Endorphins are present in cytoplasm of secretory cells.

20. Pars Posterior
Consists of numerous unmyelinated nerve fibres - axons of
neurons located in the hypothalamus.
Nerve fibres arise in the supraoptic & paraventricular nuclei.
Between axons there are supporting cells-pituicytes.
Axons descending into pars posterior from hypothalamus end
in terminals closely related to capillaries.
pars posterior release
vasopressin (ADH)- supraoptic nucleus -controls reabsorption
of water by kidney tubules.
Oxytocin- paraventricular nucleus: controls contraction of
smooth muscle of uterus & mammary gland.

21. Pituitary adenomas:
3 types according to cells of their origin.
(a) Acidophil adenoma gives rise to gigantism in children and acromegaly in adults.
(b) Basophil adenoma: gives rise to Cushing’s syndrome. Females are most affected. There is accumulation of fat on the face,
neck, and trunk
(c )Chromophobe adenoma

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