1. Chapter 19 Bone

2. A. Endocrine Control of Ca 2+ & PO 4 3-  __________________, 1,25-dihydoxy Vit D, & calcitonin control Ca 2+ and P0 4 3- levels & activities  Via effects on bone formation & ___________, intestinal absorption, & _________________

3. B. Bone Deposition & Reabsorption ____________ make bone by 1st secreting a matrix of collagen which becomes hardened by deposition of hydroxyapatite Skeleton is a storage reservoir for calcium & phosphate Bone is hardened with calcium phosphate crystals (hydroxyapatite)  _______________ reabsorb bone by secreting enzymes to dissolve matrix & hydroxyapatite

4. C. Parathyroid Hormone (PTH)  Secreted by __________________  most important hormone in control of _______ levels  Release is stimulated by low blood Ca 2+ levels  Stimulates osteoclasts to ________________  Stimulates kidneys to reabsorb Ca 2+ from filtrate, & inhibits reabsorption of P0 4 3-  Promotes formation of 1,25 Vit D 3  Many ___________ secrete PTH-related protein that interacts with PTH receptors producing hypercalcemia

5. D. Calcitonin  Secreted by ________ of thyroid gland  Works with PTH & 1,25 Vit D 3 to regulate ________ levels  Stimulated by Ca 2+  Inhibits __________ E. ______________  Causes epiphyseal discs (cartilaginous growth plates) to seal (ossify) which ____________  Is necessary for proper bone mineralization & prevention of _______________  Stimulates ______________ activity & suppresses formation of _____________

6. F. TSH & ______________  ________________are more prone to osteoporosi G. 1,25 Vitamin D3  Synthesis begins in skin when cholesterol derivative is converted to Vit D3 by ____________ Fig 19.21

7. 1,25 Vitamin D 3 continued  Directly stimulates intestinal absorption of ___________  When Ca 2+ intake is inadequate, directly stimulates bone reabsorption  Stimulates kidney to reabsorb _________________  Stimulated by PTH  Inadequate Vit D - _______________ & _________ (loss of bone calcification)

8. Overview of Hormonal Control of Ca 2+ Fig 19.23 Fig 19.24