Pituitary Gland

Question 1

Anatomy of the pituitary

Answer 1

• pea-shaped structure
• 1-1.5cm (0.5 inches) in diameter
• lies in the hypophyseal fossa of the sella turcica of the sphenoid bone.
• attaches to the hypothalamus by the infundibulum (stalk)
• has 2 anatomically & functionally separate portions:
  1. Anterior pituitary
  2. Posterior pituitary

Question 2

Sella turcica of the sphenoid bone

Answer 2

• tuberculum sellae
• hypophyseal fossa
• dorsum sellae

Question 3

Portal System

Answer 3

Blood flows from one capillary network into a portal vein, & then into a second capillary network before returning to the heart.

Question 4

Superior hypophyseal artery & Inferior hypophyseal arteries arise from the?

Answer 4

Internal carotid artery

Question 5

Hypophyseal veins & Inferior hypophyseal veins drain into the?

Answer 5

cavernous sinuses

Question 6

Hypophyseal Portal System - Pathway for Anterior Pituitary
(A - E)

Answer 6

A) Superior hypophyseal arteries bring blood into the hypothalamus (located at the junction of the median eminence of the hypothalamus & the infundibulum).
- Neurosecretory cells (clusters of specialized neurons above the optic chiasm) synthesize the hypothalamic releasing & inhibiting hormones in their cell bodies & package the hormones inside the vesicles, which reach the axon terminals by axonal transport.
- Nerve impulses stimulate the vesicles to undergo exocytosis.

B) These arteries divide into the Primary plexus of the hypophyseal portal system.

C) From the primary plexus, blood drains into the hypophyseal portal veins that pass down the outside of the infundibulum.

D) These portal veins divide again & form the secondary plexus of the hypophyseal portal system in the anterior pituitary.

E) To the anterior pituitary veins and then into the general circulation to target tissues.