Pituitary Gland

PITUITARY GLAND (HYPOPHYSIS CEREBRI)

• Pituitary gland lies within hypophyseal/pituitary fossa or sella tursica of sphenoid bone which is roofed by diaphragm sellae. 
• It is suspended from tuber cinereum of hypothalamus by infundibulum (pituitary stalk).
• It is related anterosuperiorly to optic chiasma, laterally to cavernous sinus and inferiorly to sphenoid air sinuses in the body of sphenoid.

SHAPE: Oval in shape.

SIZE: measures 8×12 mm, & weighs about 500 mg.

SUBDIVISIONS:

Has 2 main subdivisions:

1) Adenohypophysis (anterior lobe) and   2) Neurohypophysis (posterior lobe)

1. ADENOHYPOPHYSIS (Anterior lobe) include:

1. pars anterior or pars distalis or pars glandularis or anterior lobe proper
2. pars intermedia (intermediate lobe)
3. tuberal lobe (pars tuberalis)

It develops from an upward growth (Rathke’s pouch) from the ectodermal roof of stomodeum.

2. NEUROHYPOPHYSIS (posterior lobe) include:

1. pars posterior or pars nervosa or neural lobe or posterior lobe proper
2. infundibulum (infundibular stem)
3. median eminence

It develops from a downgrowth from the 3rd ventricle/diencephalon (neuroectoderm) called infundibulum.

• Anterior lobe contains many hormone secreting cells: chromophills (acidophils, basophils), chromophobes and folliculostellate cells.
• Posterior pituitary contain neuroglia like pituicytes which do not secrete any hormone.
• The posterior pituitary hormones (ADH & OXYTOCIN) are synthesised in hypothalamus and transported to posterior lobe by hypothalamohypophyseal nerve fiber tract and stored in the axon terminals of neurohypophysis in Herring bodies before their release.

BLOOD SUPPLY:

• Pituitary is supplied by a single inferior hypophyseal artery and several superior hypophyseal arteries. These hypophyseal arteries arebranches of internal carotid artery.
• Venous blood enters the adjacent cavernous & intercavernous sinuses. In addition to these vessels there is a hypothalamohypophseal portal venous system connecting the hypothalamus and neurohypophysis with adenohypophysis.

VENOUS DRAINAGE:

There are three routes for venous drainage of neurohypophysis:

1. To adenohypophysis via long and short portal vessels.

2. Into dural venous sinuses via inferior hypophysael veins.

3. To hypothalamus via capillaries passing to median eminence.

Exam Question

• Anterior pituitary develops from Rathke’s pouch.
• Posterior piyuitary develops from infundibulum.
• Herring bodies are seen in Neurohypophysis.
• Routes for venous drainage of neurohypophysis: