histo - pituitary gland
TRANSCRIPT
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Histology - Endocrine Glands
Pituitary Gland
Muhammad Ressam Nazir
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PITUITARY GLAND (The Hypophysis Cerebri)
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Pituitary gland
It lies in the base of the skull in a portion of sphenoid bone called Sella Turcica
Weight= 500-900 mg
Size is like that of pea.
It may double in size during pregnancy.
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Gross Anatomy
Because of its dual origin, the pituitary actually consists of two glands
the anterior adenohypophysis (anterior pituitary)
the posterior neurohypophysis (posterior pituitary)
Both are united anatomically but with different functions.
The adenohypophysis, derived from the oral ectoderm, has threeparts: a large pars distalis (or the anterior lobe); the pars tuberalis,
which wraps around the infundibulum; and the thin pars intermedia.
The neurohypophysis retains features of CNS tissue from which it
developed (floor of diencephalon (forebrain)) and consists of a large part, the
pars nervosa, and the smaller infundibulum with its stalk attached tothe hypothalamus at the median eminence.
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The Hypothalamic-Hypophyseal Portal System
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Histology of the Pituitary Gland
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Histology of the Pituitary Gland
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ADENOHYPOPHYSIS(Anterior Pituitary)
Pars Distalis
75 % of the hypophysis.
Main components are cords of
epithelial cells interspersed withfenestrated capillaries.
Gland is surrounded by a C.T.
capsule.
Cells of parenchyma =
chromophobes, chromophils. Stroma = composed of reticular
fibers and fibroblasts.
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Pars Distalis
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Cell Types
Chromphobes: No affinity for stains
50 % cells in the pars disatalis.
Rounded or polygonal cells
No secretory granules
Actually these are degranulated chromophils.
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Chromphils:
Remaining 50 % of the cells.
Rounded or polygonal cells
Have affinity for stains due to presence of cytoplasmic granules.
2 types: acidophils (70%) and basophils.
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Acidophils:
Larger than chromophobes but smaller than basophils
Cytoplasm has granules which stain with aciidc dyes (e.g. eosin, orange G,
azocarmine etc) Alpha acidophils (somatotropes): commoner of the two types, stain well with
orange G. Secrete GH.
Epsilon acidophils (lactotropes or mammotropes): Granules stain with
azocarmine. Secrete prolactin.
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Basophils:
Larger in size than acidophils
Dont stain with hematoxylin but stain intensely with methylene blue.
Beta basophils(thyrotropes): stain intensely with aldehyde fuchsin. secrete
TSH.
Delta cells (gonadotropes): secrete FSH and LH.
Corticotropes:these cells also dont stain with aldehyde fuchsin. They secrete
ACTH.
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Pars Tuberalis
The pars tuberalis is a funnel-shaped region surrounding the infundibulum of
the neurohypophysis.
Most of the cells of the pars tuberalis are basophilic gonadotropic cells that
secrete follice-stimulating hormone (FSH) and luteinizing hormone (LH).
Pars Intermedia
The pars intermedia is a thin zone of basophilic cells between the pars distalis
and the pars nervosa of the neurohypophysis.
MSH increases melanocyte activity and cells of the pars intermedia are often
referred to as melanotropic cells, but the overall physiological significance of
this region remains uncertain, especially in adults.
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The diagram summarizes the major hormones of the anterior pituitary and indicates their most important targets.
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NEUROHYPOPHYSIS
(Posterior Pituitary)
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NEUROHYPOPHYSIS
The neurohypophysis consists of thepars nervosa and the infundibularstalk.
The pars nervosa, unlike theadenohypophysis, does not containsecretory cells.
It is composed of neural tissue,containing some 100,000unmyelinated axons of secretoryneurons situated in the supraopticandparaventricular nuclei of thehypothalamus.
Also present are highly branched glialcells called pituicytes that resemble
astrocytes and are the most abundantcell type in the posterior pituitary. Their main role is to assist in the
storage and release of neurohypophysialhormones.
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THANK YOU
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