Parathyroid Gland Flashcards
Outline the calcium pathway in the body
Dietary intake
Absorption by digestive tract into plasma
Deposition onto bone via osteoblasts, Resorbtion vis osteoclasts
Filtration by kidneys, reabsorbtion by kidneys
Urinary loss (kidney), faecal loss (digestive tract)
Outline calcium homeostasis
Concentration of extracellular (blood) calcium is tightly controlled
Bone is body’s major store of calcium
Immediate adjustments made via rapid bone-blood exchange
Normally balance exists between buildup and breakdown of bone
What three hormones are involved in calcium regulation
Parathyroid hormone (PTH)
Calcitriol
Calcitonin
Where are the parathyroid glands located
Posterior to the thyroid
What is role of parathyroid
Secrete parathyroid hormone (PTH)
PTH is essential for life
Outline the homeostatic response to low calcium
Stimulus: low blood calcium concentration
Parathyroid gland secretes PTH
Effects: Kidneys increase calcium reabsorbtion, decrease urinary excretion of calcium. Conversion of vitamin D to calcitriol, in tern increases calcium absorption from food.
Increases bone breakdown, thus release of calcium into blood
Blood calcium levels rise, stimulus decreases, decreases PTH synthesis
Outline what a decrease in plasma [Ca2+] results in
And,
Outline what a increase in plasma [Ca2+] results in
Increase in plasma [Ca2+] leads to increase in PTH release
Decrease in plasma [Ca2+] leads to decrease in PTH release
Outline the relationship between the hypothalamus and the calcium regulation pathway
Calcium regulation pathway is not controlled by hypothalamus
What prevents exponential increase in Calcitriol in calcium regulatory system
Conversion of Vitamin D to Calcitriol, while increasing Ca2+ absorption in kidney, also acts to inhibit further Vitamin D conversion to Calcitriol, preventing exponential uptake of Ca2+
