Chapter 31- Hyphothalamus And The Pituitary Gland (Rhodes Phy) Flashcards
What comprises the anterior pituitary(adenohypoysis)?
- pars tuberalis (outer covering)
- pars distal is or “anterior lobe”
What comprises the posterior pituitary (neurohypophysis) ?
- infundibular stem (inner part of the stalk)
- infundibular process (posterior lobe)
- median eminence
Note: in most vertebrates, pars intermedia is also present
Embryo logical origin of the anterior and posterior pituitary?
Anterior pituitary = evagination of the oral ectoderm called “Rathkes pouch”
Posterior pituitary = forms as an extension of hypothalamus (composed of neural tissue)
Where are the anterior pituitary hormones secreted after being produced ?
Into blood sinusoids
Different cells producing anterior pituitary hormones?
- Corticotrophs = Adrenocorticotropic hormone or corticotropin
- Thyrotrophs = Thyroid-stimulating hormone
- Somatotrophs = Growth hormone
- Lactotrophs= Prolactin
- Gonadotrophs= Follicle stimulating & Leutinizing hormone
What regulates the secretory activity of cells that produce anterior pituitary hormones?
Hypophysiotropic hormones
What inhibits secretion of GH(somatostatin)?
Somatostatin also called as somatotrophin release- inhibiting factor
Prohormones of AVP and oxytocin are synthesized by?
In cell bodies of Magnocellular neurons
Note: from here the prohormones are sent to the axon terminals in the posterior lobe and before that during their journey, proteolytic enzymes cleave these prohormones to produce AVP and oxytocin
What acts as a functional unit in secretion of oxytocin and AVP?
Hypothalamus and Posterior Pituitary
Physiological signals stimulating release of AVP?
- rise in osmolality of blood
- decrease in blood volume
Chemical mediators of AVP release?
- catecholamines
- angiotensin ll
- atrial natriuretic peptide
Physiological activity of AVP?
- Increase water reabsorption by the collecting ducts of kidneys
- production of concentrated urine
Note: low blood AVP levels result in diabetes insipidus and excessive production of dilute urine.
Physiological functions of Oxytocin?
- help ejection of milk from the alveoli of mammary gland
- contraction of smooth muscle in the uterus during labor
Physiological actions of Adrenocorticotropic hormone (ACTH) or corticotrophin?
- stimulate production of glucocorticoids and androgens from adrenal cortex
- maintain size of zona fasiculata and zona retricularis of cortex
Physiological function of thyroid stimulating hormone?
Stimulate production of thyroid hormones T3 & T4 by thyroid follicular cells
Maintain size of follicular cells
Physiological function of growth hormone?
Stimulates postnatal body growth
Stimulates triglycerides lipolysis
Inhibits insulin action on carbohydrate and lipid metabolism
Pituitary gland is also known as?
“Master Gland”
