Calcium + Bone Homeostasis Flashcards
Thyroid hormone play what kind of role in growth?
- permissive
2. direct in nervous system development
need what for bone growth?
calcium and protein
where does hydroxyapatite bind to in bone?
collagen fiber lattice
vascular supply of bone?
very vascular
outer bone is called? purpose?
compact or cortical bone for strength
spongy bone called? filled with?
trabecular bone, open, cell-filled spaces
osteoblasts are modified?
fibroblasts
osteoblasts produce what?
enzymes and osteoid to allow hydroapatite to bind
2 other factors aid in bone deposition in osteoblasts:
osteocalcin
osteonectin
site of bone growth?
epiphyseal plate
shaft of long bone called?
diaphyses
ends of long bones called?
epiphyses
Chondrocytes’ role in bone growth?
near epiphysis, make collagen, continuously dividing column, disintegrate leaving spaces where osteoblasts can deposit hydroxyapatite
when osteoblasts aren’t active, they are called?
osteocytes
describe osteoclasts histologically
large mobile multinucleate cells from hematopoietic stem cells
osteoclasts secrete
acid and protease to dissolve calcified matrix and collagen support
3 organs involves in Calcium metabolism and control are?
bones
kidney
intestines
3 Calcium metabolism and control hormones?
PTH
Vitamin D3 (calcitriol)
Calcitonin
Calcium and cell adhesions?
important in tight junctions
how much %calcium is found in:
Bone
ECF
ICF
Bone: 99%
ECF: 0.1%
ICF: 0.9% (signalling)
most calcium lost where?
urine
where in kidney is calcium reabsorbed?
distal nephron
need parathyroid glands?
essential for life
what does PTH do to plasma calcium and phosphate?
increase plasma calcium
decrease plasma phosphate
PTH receptors in bone?
Nope. works via paracrine osteoprotegerins (OPG) and RANKL
PTH action on kidney?
reabsorb calcium
excrete phosphate
PTH actions on intestine?
indirectly increases resorption via Vitamin D activation
PTH peptide or steroid?
peptide
PTH stored?
Nope
onset of PTH on:
kidney
osteoclasts
Intestinal absorption
kidney: minutes
osteoclasts: 1-2 hours
Intestinal absorption: 1-2 days
when is calcitonin released?
only with extreme hypercalcemia
calcitonin peptide or steroid?
peptide
calcitonin affect intestine?
Nope. only bone and kidney
calcitonin is possibly protective during?
pregnancy and lactation
how to activate vitamin D? does what?
- sunlight to make Vitamin D3
- liver - add hydroxyl
- kidney - add hydroxyl
- activated and promotes intestinal absorption of Ca2+ and PO43-
Vitamin D3 peptide or steroid?
steroid
what 3 things stims Vitamin D3?
- low calcium
- indirectly via PTH
- prolactin
Vitamin D3 target organ and target in cell?
intestine
bone
kidney
nuclear target
What is the endogenour precursor to vitamin D3?
7- dehydrocholesterol
what stops long bone growth?
estrogen
phosphate movements vs. calcium movements are?
paralleled
What happens to phosphate with:
PTH:
Vitamin D3:
PTH: promotes excretion in kidneys, and resorption in bone
Vitamin D3: enhances absorption in intestines
usual cause of PTH hypersecretion?
tumour
usual cause of PTH hyposecretion?
inadvertent parathyroidectomy
Vitamin D deficiency leads to what?
poor intestinal calcium absorption
Rickets - kids
Osteomalacia - adults
osteoporosis high in what conditions?
post-menopausal women cushing's alcoholism malnutrition inactivity
preventable ris factors for osteoporosis:
dietary calcium
exercise
smoking