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Bone: Test Your Understanding (continued)
Teacher's Guide
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4. How is bone involved in maintaining calcium levels in the blood?
Osteoclast-mediated bone resorption is the mechanism for releasing calcium stored in bone for
maintaining calcium levels in the blood. The parathyroid and thyroid glands monitor the level of
calcium in the blood. If the level drops too low, the parathyroid gland releases parathyroid hormone to
prevent the loss of calcium through the kidneys and to mobilize calcium from bone. If the blood calcium
level is too high, the thyroid gland releases the hormone calcitonin, which rapidly inhibits the
resorptive activity of osteoclasts.
5. Critical Thinking: What might an individual do to reduce the risk of osteoporosis, and why?
Sample answer: To reduce the risk of osteoporosis, a person might increase their calcium intake
to reduce the need for the osteoclasts to resorb calcium from the bones, and increase load-bearing
exercises such as lifting weights, to increase the bone-building of the osteoblasts.
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