Bones and Calcium Flashcards
What is the principle reservoir for calcium and potassium?
Bone.
What is osteoporosis?
The breaking of bones due to calcium deficiency.
What is osteopenia?
Weakening of bones (not as bad as osteroporosis)
What is osteopetrosis?
The hardening of bones, causing them to become inflexible and brittle.
Why is the regulation of calcium important?
- Bone structure
- Excitability of cells
- Intracellular signalling
Where are the blood’s three sources of calcium/phosphate?
Bone, kidney, and heart.
What two hormones are most important in calcium regulation?
Vitamin D3 and PTH
What are the two cells in bone?
Osteoblasts and osteoclasts
What effect does D3/PTH have on bone?
Increases breakdown of matrix for bone resportion.
How are osteoclasts activated?
Secretion of RANK from osteoblasts after activation by PTH/D3 activates osteoclast production.
What is the net effect of PTH?
Bone: increase calcium/phosphate resorption into blood
Kidney: increase calcium absorption but increase phosphate excretion
Stimulates vitamin D processing in kidney
Why is phosphate excreted via PTH?
Calcium and phosphate form a precipitate.
How is vitamin D metabolized?
- Vitamin D3 converted to 25-OH-D3 in liver (by 25-hydroxenase)
- Forms either 1,25-OH-D3 or 24,25-OH-D3
When is 1,25-OH-D3 (CALCITRIOL) formed?
Low calcium, PTH
When is 24, 25-OH-D3 (SECALCIFEROL) formed?
High calcitriol, high calcium.