anatomy 20.3

Where is the pituitary gland located?

Inferior to the hypothalamus.

What is another name for the pituitary gland?

Hypophysis.

Where is the pituitary gland housed?

In the hypophyseal fossa within the sella turcica of the sphenoid bone.

What connects the pituitary gland to the hypothalamus?

A thin stalk called the infundibulum.

Where does the infundibulum extend from?

The base of the hypothalamus at the median eminence.

What structures are located anterior and posterior to the median eminence?

The optic chiasm is anterior, and the mammillary bodies are posterior.

What is the diaphragma sellae?

A cranial dural septum that covers the pituitary gland and ensheathes the infundibular stalk.

What is the function of the diaphragma sellae?

It restricts movement of the pituitary gland.

What are the two major structural and functional divisions of the pituitary gland?

The anterior pituitary and posterior pituitary.

What is another name for the anterior pituitary?

Adenohypophysis.

What is another name for the posterior pituitary?

Neurohypophysis.

Which part of the pituitary gland produces and secretes hormones?

The anterior pituitary.

What are the three regions of the anterior pituitary?

The pars distalis, pars intermedia, and pars tuberalis.

What is the pars distalis?

The large anterior portion of the anterior pituitary.

What is the pars intermedia?

A thin region between the pars distalis and posterior pituitary.

What is the pars tuberalis?

A thin portion that wraps around the infundibular stalk.

Why does the anterior pituitary have an extensive distribution of blood vessels?

To facilitate the uptake and transport of hormones.

How are anterior pituitary secretions controlled?

By regulatory hormones secreted by the hypothalamus.

What blood vessel network carries hypothalamic regulatory hormones to the anterior pituitary?

The hypothalamo-hypophyseal portal system.

What is a portal system?

A vascular system composed of two different capillary beds connected by portal vessels.

What are the two capillary plexuses of the hypothalamo-hypophyseal portal system?

The primary plexus in the hypothalamus and the secondary plexus in the anterior pituitary.

Where is the primary plexus located?

In the median eminence of the hypothalamus.

What is special about the capillaries of the primary plexus?

They form a very porous capillary network that allows hypothalamic hormones to enter the blood.

What artery supplies arterial blood to the primary plexus?

The superior hypophyseal artery.

What vessels drain the primary plexus and carry hypothalamic hormones toward the anterior pituitary?

The hypophyseal portal veins.

Where do the hypophyseal portal veins travel?

They extend inferiorly from the median eminence through the infundibulum to the anterior pituitary.

What happens when the hypophyseal portal veins reach the anterior pituitary?

They disperse into the secondary plexus, where hypothalamic hormones leave the blood and enter the surrounding interstitial spaces.

What happens to blood leaving the anterior pituitary?

It is drained by the anterior hypophyseal veins, carrying anterior pituitary hormones into the systemic circulation and eventually back to the heart.

What is the overall purpose of the hypothalamo-hypophyseal portal system?

It provides a direct pathway for hypothalamic regulatory hormones to reach the anterior pituitary and allows anterior pituitary hormones to enter the systemic blood.

What are tropic hormones?

Hormones that stimulate hormone secretion from other endocrine glands or cells.