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The parathyroid glands are
small, round masses of tissue attached to the posterior surface of the lateral lobes of the thyroid.
There are usually two parathyroid glands attached to each
lobe of the thyroid, one superior and one inferior
Parathyroid hormone (PTH) is secreted by the
- *Increases blood Ca2+ and Mg2+ levels by:
- - Stimulating osteoclastic activity
- - Increasing Ca2+ and Mg2+ from the GI tract by increasing levels of calcitrol (vitamin D)
*Decreases blood HPO42-
by increasing loss of HPO42-
in the urine.
Actions of Parathyroid Hormone
Increases blood calcium levels
Increases blood magnesium levels
Decreases blood phosphate levels
Increases levels of calcitriol (active from vitamin D)
Parathyroid hormone and calcitonin are
The goal of PTH is to ________ blood calcium levels. Calcitonin wants to ______ them.
There are two adrenal glands, one superior to each
Each adrenal gland consists of two regions, the
adrenal cortex and adrenal medulla
The cortex is peripherally located and makes up
80-90% of the total weight of the gland.
The adrenal medullae secrete two hormones,
epinephrine and norepinephrine, also known as adrenaline and noradrenaline
The majority of the hormone secreted is
epinephrine, about 80%
The adrenal cortex has three functional zones. What are they and what do they secrete?
-Zona glomerulosa- produces and secretes the mineralocorticoids.
- Zona fasciculata - produces and secretes the glucocorticoids.
- Zona reticularis - produces and secretes the gonadocorticoids.
CRH stimulates the release of ACTH, which in turn stimulates the release of the
The adrenal medulla secretions are very similar to the effects of the
sympathetic nervous system
-Secretes epinephrine and some norephinephrine.
-Innervated by sympathetic preganglionics.
-Acts similar to a sympathetic postganglionic
-The secretions of the medulla duplicate and prolong the sympathetic response.
Adrenal Cortical Hormones:
Mineralocorticoids help control
water and electrolyte balance.
-Aldosterone plays the larges role of the mineralocorticoids.
*Conserves Na+ and H2O through re absorption in the kidneys
*Promotes the excretion of H+ and K+ into the urine.
Most important mechanism for control of aldosterone is the RAAS
This pathway is stimulated by one or more of the following.
- -decrease in blood volume
- -Na+ deficiency
All stimuli result in a decrease in blood pressure.
The low blood pressure stimulates
juxtaglomerular cells in the kidneys to secrete the enzyme renin
Renin converts the plasma protein angiotensinogen produced in the liver into
As angiotensin I circulates to the lings, an enzyme called
ACE converts angiotensin I to angiotensin II
Angiotensin II has two effects:
Stimulates the adrenal cortex to secret aldosterone
Cortisol is a person's anti-
Effects of Glucocorticoids
Protein breakdown, mainly in muscle fibers, to free up amino acids for ATP production or synthesis of other proteins.
Stimulates liver cells to convert amino acids and lactic acid to glucos (gluconeogenesis)
Stimulates the breakdown of triglycerides to release fatty acids into the blood.
Inhibit the activity of white blood cells that participate in inflammation
Corticol is the main player of the
- in males, androgens are converted to testosterone.
- in females, the androgens are converted to testosterone and finally estrogen.
*The relatively small amount of estrogen produced from the androgens is insignificant, but after menopause, the secretion of estrogen from the adrenal gland may prove beneficial.
The androgens contribute to the development of
secondary sex characteristics in both sexes, and they promote the female libido (sex drive)