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Pituitary gland
1. Adenohypophysis
i. Pars distalis
ii. Pars tuberalis
iii. Pars intermedia
2. Neurohypophysis
Pituitary gland
The pituitary gland is very complicated endocrine gland with many crucial functions.
It is otherwise called hypophysis.
It controls all the endocrine glands, so it is called master gland.
In 16th century vesalius named the pituitary gland.
The gland is the best protected oxygen of body.
The pituitary body is attached to the hypothalamus by means of a stalk.
Shape-
It is small, oval shaped structure, situated at the base of brain, in the sella turcica at the sphenoid bone.
Size-
The pituitary gland in man measures 1.2 to 1.5 cm and average weight is 0.5 gm.
Color-
The pituitary gland is reddish-grey in colour.
Blood supply-
The blood vessels for the hypothalamus arise from superior hypophysial branches of the interior carotid arteries.
The neurohypophysis has a separated blood supply by the inferior hypophysial branches.
Anatomy-
The pituitary gland has a front and a back lobe.
The anterior lobe is called adenohypophysis and the posterior lobe is called neurohypophysis.
Divisions are distinctly different in their embryonic origin and histological structures.
1. 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.
i. Pars distalis
The part of adenohypophysis is made up of parenchymal cell.
It is of two types
A. Chromophobous
B. Chromophils
ii. 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.
iii. Pars intermedia
In pars intermedia, several layes 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.
2. Neurohypophysis
Neurohypophysis develops from neural ectoderm.
It is called posterior lobe.
The cells of neurohypophysis are called pituicytes.
These are fusiform cells.
Yellow and brown pigments are present in these cells.
They are called pituicytes of Bucy.
Granules of pituicytes are composed to unsaturated neutral fat and such, they are easily stained with asmic acid.
The hormone pass down along axon in the hypothalamus hypophysial tract into the posterior lobe of the hypophysis.
The hormones are stored in the neurohypophysis.
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