Pituitary gland

Question 1

Which anatomical features lie adjacent to or near the pituitary gland?

Answer 1

Rostrally: optic chiasma

Caudally: mammillary body and midbrain

Ventrally: Bassi crani = set of three bones that form the base of the skull. They fuse together to make a solid bottom. Within this, there is a thumb hole (sella turcica), in which sits the pituitary gland.

Laterally: venous sinuses

Question 2

Name the functional regions of the pituitary gland?

Answer 2

Adenohypophysis and neurohypophysis

Question 3

How are the adenohypophysis and nuerophypophysis regions functionally linked with the diencephalon?

Answer 3

Functionally linked with the hypothalamus. Axons come down from brain with neurohypophysis. The adenohypophysis is hormonally linked to the hypothalamus. Because the releasing factors that make the cells in the pituitary gland release their cells have come from the hypothalamus. So we have a releasing factor produced in hypothalamus, taken down into the blood stream via a capillary portal system, down into pituitary gland and get release of different factors. E.g. corticotrophin releasing factor is released by the hypothalamus, which goes down into the pituitary gland, which then releases ACTH.

Question 4

Which usually inactive region of the pituitary gland becomes problematic in older horses?

Answer 4

Pars Intermedius

Question 5

If the brain is removed from the skull, the pituitary gland usually remains in-situ. Why is this so?

Answer 5

Encased in bone & dura goes across, pituitary gland can’t be pulled through!

Question 6

There is a hypothalamic-hypophyseal portal system.

Why is it called a portal system?

Answer 6

Very long capillary bed, doesn’t join back to a vein!

Question 7

What are the embryological origins of the pituitary gland?

Answer 7

Adenohypophysis – from roof of mouth.

Upgrowth of ectoderm of roof of the developing mouth (stomodeum) – Rathke’s pouch

• Cups around developing neurohypophysis
• Connection with mouth lost

Neurohypophysis – from hypothalamus.

Downgrowth of ectoderm of forebrain – diencephalon/future hypothalamus.

Retains connection with brain – infundibulum.

Question 8

To which part of the brain does the epiphysis belong to?

Answer 8

Diencephalon

Question 9

What hormone does the epiphysis produce?

Answer 9

Melatonin

Question 10

What is the function of the epiphysis:

In day-to-day life?

In reproduction?

Answer 10

In day-to-day life? Circadian rhythms.

In reproduction? Synchronisation of seasonal breeders etc. see lecture!

Question 11

What do the anterior and posterior lobes of the pituitary produce?

Answer 11