Hypothalamo-adenohypophysial System Flashcards
What is the bony shelf that the pituitary is found in?
Sella Turcica
Describe the embryological origin of the pituitary gland.
The adenohypophysis originates from glandular tissue from the buccal cavity that extends upwards and fuses with an extension of neural tissue from the developing hypothalamus that forms the neurohypophysis. Eventually the connection to the buccal cavity is cut off.
Which ventricle is the hypothalamus located near?
3rd ventricle
What are the two areas of the brain that are useful anatomical markers for distinguishing the posterior pituitary from the anterior?
Anterior - optic chiasma
Posterior - mammilary body
What are hypothalamic nuclei?
They are groups of neuronal cell bodies that can be grouped functionally.
Where is the median eminence?
It is located between the pituitary stalk and the hypothalamus.
Describe the blood supply in the pituitary gland.
The primary capillary plexus is found in the median eminence. It is connected, via the hypothalamo-hypophysial portal system to the secondary capillary plexus in the adenohypophysis. The blood from the secondary capillary plexus drains via the cavernous sinus and out via the jugular veins.
NOTE: primary capillary plexus comes from the superior hypophysial artery
What is a key feature of the primary capillary plexus?
The capillary is fenestrated (there are small holes in it)
Describe how the hypothalamus exerts control over the adenohypophysis.
Some neurones from the hypothalamus terminate on the median eminence at the primary capillary plexus. The neurosecretions released by these neurones are hormones that travel via the hypothalamo-hypophysial system to the secondary capillary plexus where they stimulate the secretion of adenohypophysial hormones.
What are the FIVE types of adenohypophysial cells and what hormones do they produce?
Somatotrophs - somatotrophin Lactotrophs - prolactin Gonadotrophs - LH and FSH Thyrotrophs - Thyrotrophin Corticotrophs - corticotrophin (ACTH)
What are the THREE types of adenohypophysial hormone? Give examples of each.
Protein - somatotrophin + prolactin
Glycoprotein - FSH + LH + thyrotrophin
Polypeptide - ACTH
NOTE: Glycoproteins have an alpha chain and a beta chain. They all have the same alpha chain but have different beta chains.
State the EIGHT hypothalamic hormones and the adenohypophysial hormones that they control.
Somatotrophin releasing hormone + somatostatin = somatotrophin
Dopamine + Thyrotrophin releasing hormone = prolactin
Gonadotrophin releasing hormone + gonadotrophin inhibitory hormone = FSH + LH
Thyrotrophin releasing hormone = thyrotrophin
Corticotrophin releasing hormone + vasopressin = corticotrophin
State the tissues that the FIVE adenohypophysial hormones act on.
Somatotrophs - most cell (hepatocytes in particular) Prolactin - breasts in lactating women Gonadotrophin - gonads Thyrotrophin - thyroid Corticotrophin - adrenal cortex
Describe the two modes of action of somatotrophin.
Somatotrophin can act directly on tissues by binding to somatotrophin receptors or it can act on hepatocytes and stimulate hepatocytes to produce IGF 1, which is particularly important in growth
What are the metabolic actions of somatotrophin?
Somatotrophin stimulates amino acid transport into cells, stimulates protein synthesis, increases cartilaginous growth, stimulates lipid metabolism leading to increased fatty acid production and decreased glucose utilisation resulting in increased blood glucose concentration.
