i. Pars distalis
ii. Pars tuberalis
iii. Pars intermedia
Adenohypophysis-
Adenohypophysis is developed from the oral ectoderm.
It is divisible into 3 parts
i. Pars distalis
ii. Pars tuberalis
iii. Pars intermedia
Pars distalis, pars tuberalis, pars intermedia consists of the anterior lobe of pituitary gland.
1. Pars distalis
The part of adenohypophysis is made up of parenchymal cell.
It is of two types
A. Chromophobes
The important character of these cells are they apper in groups near the centre of cord.
In ordinary preparation, the cell membrane are not distinguishable.
Secretory granules are mostly absent.
They do not secrete any hormone.
They give rise to other types of cells.
B. Chromophylls
In chromophylls again two cells are found. They are
a. Acidophills
These are readily stained with acid dyes. It is of two types.
i. Somatotroph or somatotrophic cells
The round and ovoid in shaped cells are the secrerory cells.
They are present in very high concentration.
The cytoplasm is packed up with dense granules which are 350 to 400 micrometers in size.
They are concerneol with the secretion of growth hormone (GH).
ii. Lactotrophs or lactotrophic cells
These are secretory cells having great affinity for carmine strain.
The granules are of larger size in comparision to that of somatotrophs.
These cells are concerned with the secretion of prolactin.
b. Basophill cells.
It can be readily stained with basic dyes.
It is of three types.
i. Gonadotrophs
Gonadotrophs comprises the interstitial cells of stimulating hormone cells or leutinizing hormone cells.
These are very small and rounded or polygonal in shape.
There is a very littile amount of cytoplasm.
The secretory granules are not more than 100-300 micro meter in diameter.
It also comprises the follicle stimulating hormones.
These cells are large and rounded.
ii. Thryotrophs
These are polygonal cells with small nucleus.
They have affinity for PAS-strain.
They have large secretory granules and enlarged endoplasmic reticulum.
They secrete thyroid stimulating hormone.
iii. Corticotrophs
These are of different shapes and size.
They are small and oval cells with tubules.
The nucleus is rounded, eleptical or pear shaped.
Endoplasmic reticulum is mostly diffused.
The cells secret adrenocorticotrophic hormone to stimulate the adrenal cortex.
They also secrete melanocyte stimulating hormone.
2. Pars tuberalis
Pars tuberalus surrounded the infundibular stalk and is close to tuberinerium.
It consists of corok of compressed and glandular cells which are cuboidal.
The cytoplasm of the cells fainty basophilic.
This part of pituitary is highly vascular.
Pars tuberalus develops as a couple of lateral lobes like extension of the embryonic pars distalis.
3. Pars intermedia
In pars intermedia, several layer of polygonal cells are present.
They can be easily stained with basic dyes.
Secretory granules are present.
This layer is not vascular.
Menanocyte stimulating hormone is mainly secreted by basophilic cells of pars intermedia.
A peptide beta lipotropin is also secreted by basophilic cells of pars intermedia.
Alpha MSH and beta MSH is present in several mammals.
MSH is concerned with the dispersal of pigment cells of the skin.
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