The pituitary gland:

Question 1

AKA

Answer 1

The hypophysis

Question 2

Embryology: Development of pituitary gland

Answer 2

• Consists of 2 types of tissue

1. Early in embryonic development, a finger of ectoderm grows upward from the roof of the mouth = Rathke’s pouch
   – develops into ant. Pituitary gland. (adenohypophysis)
2. At same time the rathke’s pouch is developing, another finger of ectodermal tissue evaginates ventrally from the diencephalon (FB)
   
   • Post pituitary gland comes from same structure that the hypothalamus divides from
3. Extension of the ventral brain becomes the post-pituitary gland (neurohypophysis)
4. Ultimately, the 2 tissues grow into one another and become tightly opposed, but their structures remain distinctly different (differ in embryological origins)

Summary:
1. Extension of diencephalon – infundibulum
2. Ectodermal outpocketing of buccopharyngeal membrane – Rathke’s pouch

Question 3

Question 4

The pituitary gland is a

Answer 4

Pea-sized oval structure

Question 5

The pituitary gland is suspended from the

Answer 5

under side of the brain via the pituitary stalk (AKA infundibulum)

Question 6

The pituitary gland sits within a small depression in the

Answer 6

sphenoid bone = sella turcica

Question 7

diaphragm sellae

Answer 7

Sup surface of gland is covered with reflection of the dura matter = diaphragm sellae
This membrane has a central opening that allows passage of the infundibulum

Question 8

Key anatomical relations:

Answer 8

Ant: sphenoid sinus
Post: Posterior intercavernous sinus and dorsum sellae (post wall of sella turcica)
Sup: Diaphragm sellae (fold of dura matter as well as optic chisma)
Inf: sphenoid sinus
Lat: cavernous sinus

Question 9

Anatomically the pituitary gland is a 2-in-1 structure

Answer 9

Consisting of Ant. Pituitary and post pituitary
- have different embryonic origins and functions

Question 10

Anterior/adenohypophysis is composed mostly of

Answer 10

glandular tissue, makes it different from post pit.

Question 11

Anterior/adenohypophysis secretes

Answer 11

a number of hormones

Question 12

Anterior/adenohypophysis is divided into 3 parts

Answer 12

Pars distalis - the largest section

Pars tuberalis - a collar of tissue that usually surrounds the infundibular stalk

Pars intermedia - a narrow band that is usually separated from the pars distalis by a hypophyseal cleft

Question 13

Release of hormones from ant lobe

Answer 13

is under control of hypothalamus, which communicates with the ant pit lobe, via neurotransmitters that is secreted into the hypophysial portal vessels
These vessels ensure that hypothalamic hormones remain concentrated, rather than being diluted in systemic circulation.

Question 14

Neurohypophysis/Posterior consists mainly of

Answer 14

nervous tissue (develops from diencephalon)
- Mainly neuronal projections extending mostly from the supraoptic and paraventricular nuclei of the hypothalamus

Question 15

Neurohypophysis/Posterior secretes 2 hormones

Answer 15

ADH and oxytocin

Question 16

ADH and oxytocin are produced by

Answer 16

the nuclei of the hypothalamus and then they are stored in the post pit gland.

Question 17

Does the post pituitary gland synthesize any hormones?

Answer 17

No, only stores and releases from axons of hypothalamus neurosecretory cells.
- These axons release peptide hormones into the capillaries of the hypophyseal circulation
- These are then stored in neurosecretory vessels, before being secreted by the posterior pit. Into systemic circulation

Question 18

The post pituitary gland is a

Answer 18

Direct extension of the hypothalamus

Question 19

Neurohypophysis/Posterior consists of three parts:

Answer 19

Pars nervosa - the bulk of the posterior pituitary

Median emminence - the upper section of the neurohypophysis above the pars tuberalis

Infundibular stalk - the “stem” that connects the pars nervosa to the base of the brain

Question 20

Question 21

Arterial supply of the anterior pituitary gland

Answer 21

• Receives arterial blood supply from the superior hypophyseal artery
  (branch of internal carotid artery)
• The vessel first forms a capillary network around the hypothalamus
• Blood from this network is transported to a second capillary plexus surrounding the ant. Pit. Gland.
  = Hypothalamo hypophyseal portal system
• This system allows the hypothalamus to communicate with the ant pit gland via the release of neurotransmitters into the blood stream.

Question 22

Arterial supply of the post pit gland and the infundibulum:

Answer 22

• Receives a rich blood supply from many arteries
• Superior hypophyseal artery, infundibular artery and the inferior hypophyseal artery

Question 23

Vasculature of the pituitary gland:

Answer 23

• Is complex and unique
• While the ant and post lobe have the same venous drainage (anterior and posterior hypophyseal veins)
• They have individual arterial supply