week 9 bibc

week 9 bibc - Bone Reservoir of Ca2 and Pi-compact...

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Bone : Reservoir of Ca2+ and Pi -compact bone (shaft) and trabecular bone (ends) -Three types of cells: -Osteocytes : occupy canal in bones; sensing the stress -Osteoblasts: stimulate -have receptors for both PTH and calcitriol -produce , a mixture of collagen and other extracellular matrix proteins deposit bone formation -secrete MCSF -express RANK-ligand, which binds to receptor in osteoclast (RANK) stim. OC -secrete under the influence of ; blocks RANK-L no activation of osteoclast cells -Osteoclast: bone -regulated by osteoblasts -express RANK receptor -mechanism: Activation of RANK receptor OC migrate and attach to surface of the bone forms which has lots of proton pumps (H+/K+-ATPase) pH in the cavity between bone and OC’s tight junction drops (pH~4) acidity breaks down hydroxyapatite and dissolves bones simultaneously secrete collagenases which breaks down extracellular matrix and dissolves bones release Ca2+ and Pi Adrenal Cortex Zona glomerulosa:outermost layer -do not have 17- α -hydroxylase (necessary to make glucocorticoids and androgens) -secretes mineralocorticoids, mainly aldosterone -main target – kidney, sweat gland Zona fasciculata: middle layer Zona reticularis: innermost layer These layers do have 17- α -hydroxylase and secrete glucocorticoids(cortisol) and androgens (DHEA, DHEA-S, androstnedione) -cortisol, a glucocorticoid, can bind and stimulate both gluco and mineralocorticoid receptor, but aldosterone, a mineralocorticoids, can bind only to mineralocorticoid receptor. -in males, androgens secreted by cortex are less than 5% of total androgens (mainly from testis)
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This note was uploaded on 04/06/2012 for the course BICD 150 taught by Professor Fortes during the Winter '09 term at UCSD.

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week 9 bibc - Bone Reservoir of Ca2 and Pi-compact...

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