W28-L5: Bone and Calcium Homeostasis Flashcards
What do chondrocytes produce?
Collagen
What hormones are involved in control of Ca2_ metabolism?
- Parathyroid hormone (PTH)
- Vitamin D3 (calcitriol)
- Calcitonin
What other aspects of Ca2+ regulation do hormones control?
- Absorption in the small intestine
- Loss in urine
What is parathyroid hormone secreted in response to?
Decreased calcium
What are the actions of parathyroid hormone?
On bone: Increase calcium and phosphate release
On kidney: Increase ca reabsorption, decrease phosphate reabsorption
Intestine: Indirectly increases ca and phosphate reabsorption via Vit. D
When is calcitonin released?
When plasma Ca2+ is high
What are the effects of calcitonin?
Decreases plasma and phosphate via bone and increasing renal ca excretion
How does PTH interact with Vit D?
PTH turns on liver enzymes that add the first hydroxl group to vit D2
How does Vit D work?
Increases intestinal transport of Ca
Which systems are the quickest in ca regulation?
kidney effect is quick, intestine is longer and bone is longest
What hormone controls epiphysial closure?
Oestrogen
What causes PTH hypersecretion?
Tumour
What causes PTH hyposecretion?
Autoimmune attack of glands
What occurs in Vit D deficiency?
Impaired intestinal ca absorption, PTH maintains calcium at expense of bones
Why can’t PTH levels regulate Ca in Vit D deficiency?
you still need the vit D substrates if you are Vit. D deficient
