D’YOUVILLE COLLEGE
BIOLOGY 108/508 - HUMAN ANATOMY & PHYSIOLOGY II
LECTURE # 8
ENDOCRINE SYSTEM II
4.
Selected Glands and Their Products (continued):
Hypophysis (continued):
• neurohypophysis (table 16 – 1)
- oxytocin causes smooth muscle contraction in uterine wall to promote
parturition, and in ducts of mammary glands to promote milk ejection
- antidiuretic hormone (ADH) promotes water retention by the kidney
• neurohypophysis is composed of pituicytes (like neuroglia), and is
technically not an endocrine tissue, but a site for release of neurohormones of
hypothalamus via hypothalamo-hypophysial tract (fig 16 – 5a)
Thyroid Gland (fig. 16 – 8):
• thyroxine stimulates metabolic rate; it is stored inside follicles as colloid
(fig. 16 – 9); secretion is controlled by TSH from anterior pituitary
• calcitonin is a hypocalcemic hormone, from parafollicular C cells; it
inhibits osteoclasts that mobilize calcium from bone, and promotes calcium uptake
and incorporation into bone (bone sparing effect)
Parathyroid Glands (figs. 16 – 11 & 16 – 12):
• parathormone (PTH) is a hypercalcemic hormone; it raises blood calcium
by causing bone resorption by osteoclasts, by promoting intestinal absorption
(collaboration with vitamin D), and promoting kidney retention of calcium
Adrenal Glands (figs. 16 – 13 & 16 – 14):
a. cortex: produces steroids:
• glucocorticoids (cortisol) have a glucose sparing effect on
carbohydrate metabolism; they are also anti-inflammatory; secretion is controlled by
ACTH from the anterior pituitary
• mineralocorticoids (aldosterone) promote sodium retention and
potassium excretion in the kidney; their secretion is controlled by the reninangiotensin system (in kidney), and by elevated blood level of potassium
• gonadocorticoids (produced in small amounts) may be responsible for
onset of puberty (preceding gonadal output of sex steroids); excess produces
adrenogenital syndrome
b. medulla: produces catecholamines:
• epinephrine produces cardioaccelerator activity (alpha receptor
mediated); it also stimulates muscle metabolism, hyperglycemia, and blood flow
(beta receptor mediated)
• norepinephrine produces vasoconstrictor and cardioaccelerator
activity (alpha receptor mediated)
Pancreatic Islets:
• insulin (insula = island) is known as the “feasting hormone”; it is
essential for glucose uptake and storage (mainly by liver); a deficiency causes
diabetes mellitus
• glucagon is a hyperglycemic hormone; it stimulates glycogenolysis and
gluconeogenesis by liver, both causing an elevation of blood glucose
Gonads: to be discussed with reproductive system