Pituitary Gland

Question 1

Neurohypophysis

Adenohypophysis

Answer 1

Neurohypophysis: Median emminence, infundibular stalk (upper and lower), pars nervosa (post lobe)

adenohypophysis: pars tuberalis, pars distalis (ant lobe)

Question 2

Where does the pituitary sit

covering?

Answer 2

In the middle of the head, in the sphenoid bone.
Pituitary fossa, with the rounded bits of the sphenoid bone (sella turcica) encasing.

To gain entry to (surgery) through nose then through bone of sphenoid sinus then there.

Covered by dura around it but also splits around the stalk. Diaphragma sella

Question 3

What is the origin of the anterior and posterior pituitary?

Answer 3

Rathke’s pouch

Anterior pituitary epithelial origin
Posterior pituitary neural origin

Question 4

Blood supply to the hypothalamus/pituitary

Long and short axons

Answer 4

The superior and inferior hypophyseal arteries that come off the internal carotid

Sup.: forms a capillary bed in the top of the infundibular stalk. Connecting with long portal vessels to the pars distalis. (short axons)

Inf.: Feeds vessels to the bottom of the stalk for short portal vessels and the posterior pituitary. (long axons)

Question 5

What is different about the trabecular artery

Answer 5

Runs from sup. hypophyseal to the lower capillary bed, not the upper.

Question 6

What can be said about the pars distalis, median emminence and pars nervosa supply?

Answer 6

Does not have direct arterial supply, however ample venous drainage.

Median emminence has arterial supply but not good venous drainage other than portal system to pars distalis.

pars nervosa: Has its own arterial (inf) and venous drainage

Question 7

Does blood run from the pituitary back to the hypothalamus?

Answer 7

Yes, short feed back loops

Question 8

How does the axis function?

Answer 8

Neurons produce and secret hormones.

• Neurohypophysis: neurons secrete hormones directly into systemic circulation in the pars nervosa (PP)
• Adenohypophysis: hormones for anterior pituitary go via portal vessels.

Tanycytes (hormone to CSF, then tanycyte to portal vessel)

Question 9

What are the cells of the pars distalis?

Answer 9

Chromophils and chromophobes

Chromaphils- acidophils and basophils

Acidophils: Somatotrophs (GH); lactotrophs (PRL)
Basophils: Gonadotrophs (FSH,LH); Thyrotrophs (TSH); Corticotrophs (ACTH)

Question 10

Pituitary cell staining with PAS or OG

clinical correlates

Answer 10

Basophils: Magenta (glycoprotein)
Acidophils: Orange (protein)

Corticotrophs do not stain

Pregnancy: marked raise of acidophils (prolactin)
Acidophil tumours (acromegaly with GH)
Basophil adenoma: Cushings, excess ACTH

Question 11

Hypothalmic hormone and ant pituitary subset

GnRH, TRH, GHRH- somatolibrien; somatostatin; PIF- dopamine; CRF

Answer 11

GnRH stimulates LH and FSH
TRH stimulates TSH
GHRH (somatoliberin) stimulates GH
Somatostatin inhibits GH
PIF (dopamine) inhibits Prolactin
CRF stimulates ACTH