Endocrine System - Pituitary

Question 1

What are the embryological origins of the Anterior/Posterior pituitary?

Answer 1

Anterior - Oral ectoderm (roof of mouth, Rathke’s pouch)

Posterior - Neural Ectoderm

Question 2

What sort of tissues are the Adenohypophysis and the Neurohypophysis?

Answer 2

Adenohypophysis: glandular epithelial tissue

Neurohypophysis: nervous tissue

Question 3

What are the parts of the Adenohypophysis?

Answer 3

Pars Distalis
Pars Intermedia
Pars Tuberalis

Distalis and Intermedia = 2/3 of lobe
Tuberalis = remaining 1/3 of lobe

Question 4

What are the parts of the Neurohypophysis?

Answer 4

Pars Nervosa

Infundibulum

Question 5

How are the components of the Adenohypophysis derivatives of Rathke’s pouch (embryological origin).

Answer 5

Distalis (thickened anterior wall of pouch)
Intermedia (remnant of posterior wall of pouch)
Tuberalis (thickened lateral walls of pouch)

Note: Pars Intermedia will have remnants of Rathke’s Pouch

Question 6

What is the function of the Infundibulum?

Answer 6

It connects the Pars Nervosa to the nervous system. It contains ONLY axons that terminate in the Nervosa.

Question 7

What is the blood supply of the Pituitary gland?

Answer 7

Internal Carotid artery

• Superior hypophyseal artery for anterior lobe
• inferior hypophyseal artery for posterior lobe

Question 8

Describe the blood pathway in the Adenohypophysis.

Answer 8

Internal Carotid -> Superior Hypophyseal artery -> Primary Capillary Plexus -> Hypophyseal Portal Veins -> Secondary Capillary Plexus -> Exit lobe via Hypophyseal Veins

Note: Pars Distalis has no real ARTERIAL blood supply.

Question 9

Describe the blood pathway in the Neurohypophysis.

Answer 9

Internal Carotid -> Inferior Hypophyseal artery -> Capillary Plexus -> Exit via Hypophyseal veins

Note: The Inferior Hypophyseal arteries enter the Pars Nervosa DIRECTLY.

Question 10

Describe the endocrine secretion of the Adenohypophysis.

Answer 10

Neurons for Pars Distalis are in the 3rd Ventricle.

• Produce Releasing/Inhibiting factors and send to Primary Capillary Plexus
• Factors will then make it to the Pars Distalis, which will respond accordingly.
• If hormones are released, they will be released into the Secondary Capillary Plexus, then into the Collecting Vein via the Hypophyseal Veins.

Question 11

Describe the endocrine secretion of the Neurohypophysis.

Answer 11

Neurons for the Pars Nervosa are in the Thalamus

• Produce hormone directly.
• Send hormones down axons and into the blood stream of the Pars Nervosa.
• Hormones will enter bloodstream.

Question 12

What are the cell types of the Pars Distalis?

Answer 12

Acidophils (40%)
Basophils (10%)
Chromophobes (50%)

Question 13

What are the hormones produced by acidophils? What are their functions?

Answer 13

Prolactin

• promote secretion of progesterone
• initiate milk formation
• promotes development of mammary

Growth Hormone
- …dude.

Question 14

What are the pathologies involving Growth Hormone?

Answer 14

Too much = Gigantism

Too little = Dwarfism

Question 15

What are the hormone produced by basophils? What are their functions?

Answer 15

FSH

• stimulate growth of ovarian follicles and estrogen secretion
• activate spermatogenic epithelium and stimulates Sertoli Cells

LH

• promotes ovulation, corpus luteum formation, progesterone secretion
• stimulate Leydig cells of testes to secrete testosterone

ACTH
- stimulate adrenal cortex to secrete glucocorticoids and gonadocorticoids

TSH

• stimulate growth of thyroid epithelial cells
• stimulate production and release of thyroid hormones

Question 16

How is the Pars Distalis regulated in terms of producing and releasing hormones?

Answer 16

• releasing/inhibitory hormones from hypothalamus (supraoptic nucleus)
• small direct effect of hormones from target organs on median eminence and distalis

Question 17

What are some of the releasing/inhibitory hormones?

Answer 17

STIMULATORS

• Thyrotropin RH: stimulate dopamine release
• Growth Hormone RH (GHRH): stimulate GH release
• Gonadotropin RH (Low frequency pulses): stimulate FSH release
• GRH (High frequency pulses): stimulate LH release

INHIBITORS
Dopamine - inhibit prolactin release
Somatostatin - inhibit GH release

Question 18

What hormones are released via the Neurohypophysis?

Answer 18

ADH/Vasopressin

Oxytocin

Question 19

What are the cell types of the Pars Nervosa?

Answer 19

Terminal endings of Axons
- Note the Herring Bodies
Pituicytes

Question 20

Where do the Neurohypophysis hormones come from?

Answer 20

Herring Bodies of the axon terminal endings.

Question 21

What brings the hormones to the Pars Nervosa for release?

Answer 21

Neurophysin I and II

I = Oxytocin
II = ADH

Question 22

What is a potential symptom of a tumor growing on the pituitary?

Answer 22

Loss of vision on one side due to tumor pressing on the optic chiasm