Parathyroid Glands Flashcards
What do the parathyroid glands do?
regulate blood Ca concentration
What is the normal blood Ca concentration?
normal total blood Ca2+ = 2.2 - 2.6 mM
What is hypocalcaemia?
low level of Ca in blood
- lethal
What is hypercalcaemia?
high level of Ca in blood
- non-lethal
- kidney stones
- fatigue
How is blood Ca concentration regulated?
Hormonal regulation:
- parathyroid hormone
- calcitonin
- 1,25-dihydroxycholecalciferol (1,25-DHCC)
What organs regulate blood Ca concentration?
- intestines
- kidney
- bone
How do the organs regulate blood Ca concentration?
intestines: uptake and secretion of Ca2+
kidneys: reabsorption and excretion of Ca2+
bones:
- movement between bone and ECF (extracellular fluid)
- osteoblast
- osteoclast
What are osteoblasts and osteoclasts?
osteoblasts: cells that form bone tissue (stores Ca2+ in bone)
osteoclasts: cells that mobilises Ca2+ from bone
Where are the parathyroid glands located and what do they secrete?
- embedded in posterior surface of thyroid gland
- synthesize & secrete parathyroid hormone (PTH)
When is PTH secreted and why?
In response to low blood Ca2+ to increase it
How does PTH increase blood Ca2+ in the organs?
bone: stimulates osteoclast / inhibits osteoblast
kidney: increase Ca2+ reabsorption in the kidney
intestines: activation of 1,25-DHCC in the kidney which stimulates Ca2+ uptake in gut
Where are C-cells located and what do they secrete?
- between follicles of the thyroid gland
- synthesize and secrete calcitonin
Why do C-cells secrete calcitonin?
In response to high blood Ca2+ to decrease it
How do C-cells decrease blood Ca2+ in the bone?
inhibition of osteoclasts
