9. ๏ Superior-
a) Diapragma sellae
b) Optic chiasma
c) Tubercinerium
d) Infundibular recess of 3rd ventricle
๏ Inferior-
a) Irregular venous channels Between two Layers
Of Dura Mater
b) Hypophyseal fossa
c) Sphenoidal Air sinuses
10.
11. ๏ On Each Side- Cavernous sinus & Structures passing
through it
12. Presenting parts
๏ The pituitary has two major parts
๏ Anterior Lobe / Adenohypophysis
๏ Posterior Lobe / Neurohypophysis
๏ Differ in their Origin, Structure & Function
13.
14. Anterior Lobe / Adenohypophysis
๏ Ectodermal derivative of the stomatodeum.
๏ Highly cellular.
๏ Pars Anterior (Pars Distalis Or Glandularis).
๏ Pars Intermedia.
๏ Pars Tuberalis.
15. Histology
๏ Clusters of epithelial cells surrounded by reticular
fibers
๏ Sinusoids & Fenestrated capillaries
๏ Glandular cells are arranged in irregular clumps or
cords between a network of capillaries
๏ Types of cells
chromophobe cells
chromophil (acidophil and basophil ) cells.
16. chromophobe cells
๏ 50% of population
๏ Inactive precursor or degranulated after release of
their most of hormonal content
๏ EM shows few granules inside.
17. Chromophil cells
๏ 50 % population
๏ Contains cytoplasmic granules
๏ The contents of the secretory vesicles are responsible
for the staining characteristics of the chromophil cells.
A. Acidophil cells (or acidophils)
B. Basophil cells (or basophils)
18. A) Acidophil cells (or acidophils)
๏ 40 % of parenchyma
๏ Stains with Eosin, Acid Fuschin, Orange G of
Azan, azocarmine
๏ frequent subtype of acidophils are the somatotrophs
(stained with the dye orange G).
๏ Somatotrophs produce growth hormone (GH or
somatotropin), which e.g. stimulates liver cells to
produce polypeptide growth factors which stimulate
growth (e.g. somatomedin which stimulates
epiphyseal cartilage )
๏ overproduction of this hormone may result in
gigantism or acromegaly
19. ๏ Mammotrophs (or lactotrophs) , the second group
of acidophils, secrete prolactin. Their number
increases significantly in late pregnancy and the early
months of lactation
20. B) Basophil cells (or basophils)
๏ 10 % of Parenchyma
๏ Stains poorly with Haematoxylin
๏ PAS staining
๏ Secrete Trophic hormones
Thyrotrophs produce thyroid stimulating hormone
(TSH or thyrotropin).
Gonadotrophs produce follicle stimulating hormone
(FSH), which stimulates the seminiferous epithelium
in males in addition to early follicular growth in
females. Gonadotrophs also produce luteinizing
hormone (LH), which stimulates production of
testosterone by Leydig cells in males in addition to late
follicular maturation, oestrogen secretion and
formation of corpus luteum in females.
21. Corticotrophs (or adrenocorticolipotrophs) secrete
adrenocorticotropic hormone (ACTH or corticotropin)
and lipotropin (LPH, no known function in humans).
๏ Corticotropes are the most frequent cell type in the
pars intermedia.
๏ In the pars intermedia, the precursor of ACTH and
LPH undergoes further hydrolysis into melanocyte
stimulating hormone (MSH, increased pigmentation
in patients with Addison's disease) and a number of
other peptides (among them endogenous opioids
e.g endorphin ).
22.
23. Posterior Lobe / Neurohypophysis
๏ Neurohypophysis is a diencephalic downgrowth
connected with the hypothalamus
๏ Neural Lobe Or Pars Posterior
๏ Median Eminence
๏ Infundibular Stem
24. ๏ consists of unmyelinated nerve fibers derived from
neurosecretory cells of the supraoptic &
paraventricular hypothalamic nuclei and
pituicytes.(Near the posterior lobe, astrocytes are
replaced by pituicytes )
๏ oval or round nuclei of the pituicytes are visible
๏ Hypothalamic nerve fibers typically terminate close to
capillaries
๏ Herring bodies - Scattered, large, and bluish-violet
(in PAS/Orange G stained sections) masses represent
dilations of these nerve fibers .
๏ Contain neurosecretory products of the hypothalamic
cells.
25.
26. ๏ In early fetal life the neurohypophysis contains a cavity
continuous with the third ventricle
๏ Axons arising from groups of hypothalamic neurones
(e.g. the magnocellular neurones of the supraoptic and
paraventricular nuclei) terminate in the
neurohypophysis.
๏ The long magnocellular axons pass to the main mass
of the neurohypophysis
๏ They form neurosecretory hypothalamohypophyseal
tract and terminate near the sinusoids of the posterior
lobe.
27. ๏ Some smaller parvocellular neurones in the
periventricular zone have shorter axons, and end in
the median eminence and infundibular stem among
the superior capillary beds of the venous portal
circulation.
๏ These small neurones produce releasing and
inhibitory hormones, which control the secretory
activities of the adenohypophysis via its portal blood
supply.
28. ๏ The neurohormones stored in the main part of the
neurohypophysis are vasopressin (antidiuretic
hormone; ADH), which controls reabsorption of water
by renal tubules , and oxytocin, which promotes the
contraction of uterine smooth muscle in childbirth
and the ejection of milk from the breast during
lactation.
๏ Storage granules containing active hormone
polypeptides bound to a transport
glycoprotein, neurophysin, pass down axons from their
site of synthesis in the neuronal somata. The granules
are seen as swellings along the axons and at their
terminals, which can reach the size of erythrocytes
29. Development
๏ Prior to neurulation cell populations which give rise to
these two portions of the pituitary gland are found
next to each other within the rostral portion of the
floor of the neural plate and the contiguous midline
neural fold.
๏ Asneurulation proceeds the future neurohypophysis
remains within the floor of the prosencephalon. The
cells of the future adenohypophysis are displaced into
the surface ectoderm, where they form hypophyseal
placode in close apposition and adherent to the
overlying prosencephalon.
30.
31. ๏ development of the adenohypophysis progresses by the
ingrowth of a mesenchymal stroma. Differentiation of
epithelial cells into stem cells and three differentiating
types is said to be apparent during the early months of fetal
development.
It has been suggested that different types of cells arise in
succession, and that they may be derived in differing
proportions from different parts of the hypophyseal recess.
๏ A craniopharyngeal canal, which sometimes runs from the
anterior part of the hypophyseal fossa of the sphenoid to
the exterior of the skull, is often said to mark the original
position of the hypophyseal recess.
๏ Traces of the stomodeal end of the recess are usually
present at the junction of the septum of the nose with the
palate.
32. ๏ Just caudal to, but in contact with, the
adenohypophyseal recess, a hollow diverticulum
elongates towards the stomodeum from the floor of
the neural plate just caudal to the hypothalamus this
region of neural outgrowth is the
neurohypophysis.
33.
34.
35. ๏ 3rd week- hypophyseal diverticulum
๏ 5th week โ diverticulum elongates & lower end
constricted
๏ 6th week- connection with oral cavity cut off.
๏ At birth the hypophysis is about one-sixth the weight
of the adult gland
๏ about one-half the weight of the adult gland at 7 years,
๏ attains adult weight at puberty.
๏ Throughout postnatal life the gland appears larger in
females, in both size and weight.
37. Hypothalamic control
๏ Hypophysiotropic area of hypothalamus
๏ Cresentic band- from preoptic area to arcuate nucleus
๏ Axons of neurons from this area conveys releasing or
inhibitory hormones to fenestreated upper radicals of
portal vessels in median eminance & infundibular
stem
38. ๏ TRH- secreated by dorsomedial nucleus
๏ LHRH- Preoptic area & anterior hypothalamus
๏ CRH- supra-optic & paraventricular nucli
๏ GRH- Ventero-medial nucleus
๏ GIH(Growth Inhibiting Hormone)- periventricular
nucleus
๏ PRH-location is nt yet known
๏ PIH- Arcuate nucleus, dopaminargic. Dopamine
inhibits Prolactin release
39. Pharyngeal hypophysis
๏ A small collection of adenohypophyseal tissue lies in
the mucoperiosteum of the human nasopharyngeal
roof
๏ By 28 weeks in utero it is well vascularized and capable
of secretion, receiving blood from the systemic vessels
of the nasopharyngeal roof. covered posteriorly by
fibrous tissue
๏ This is replaced in the second half of fetal life by
venous sinuses, and a transsphenoidal portal venous
system develops
๏ The peripheral vascularity of pharyngeal hypophysis
persists until about the fifth year
๏ Though it does not change in size after birth in
males, in females it becomes smaller, returning to
natal volume during the fifth decade
40. ๏ Reserve of potential adenohypophyseal tissue
๏ may be stimulated, particularly in females, to
synthesize and secrete adenohypophyseal hormones
in middle age, when intracranial adenohypophyseal
tissue is beginning to fail.
41. Applied Anatomy
Effect of pressure
1. Sella turcica enlarged- headache due to stretching of
dura
2. Nasal discharge if sphenoidal sinus involved
3. Upward spread- pressure on optic chiasma-
bitemporal hemianopia
4. Obesity- Frohlichโs Syndrome ( involvement of satiety
centre in hypothalamus)
5. Raised CSF Pressure
6. Exopthalmos & Opthalmoplegia
42. Disturbance of endocrine function
1. Adenoma of acidophils- giagantism in childrens ,
acromegaly in adults
2. Basophil adenoma โ cushing syndrome ( excess
ACTH)
3. Chromophobe adenoma โ hypopituitarism
4. Post. Lobe โ diabetes insipidus
