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1、.1Bob ZhengWuhan University.2Bone replacement is the replacement of old bone tissue by new bone tissueNever metabolically at restReplacing itself throughout adult life.3Remodeling allows worn or injured bone to be removed and replaced with new tissue.4Remodeling allows bone to serve as the bodys sto
2、rage area for calciumConstant supply of Ca2+ in the blood stream needed for: Transmission of nerve impulses Muscle contraction Blood coagulation Cell division .5Osteoclast and osteoblast.6Sufficient quantities of calcium(Ca) and phosphorus(P).7Sufficient amounts of vitamins, particularly vitamin D.8
3、Proper amounts of the hormonesGrowth hormone(GH), Calcitonin(CT), Parathormone(PTH), Sex hormones.9Secreted by the pituitary gland , responsible for general growth of bones Too much GigantismToo little Dwarfism.10CT is produced by the thyroid gland, inhibits osteoclastic activity PTH is secreted by
4、the parathyroid glands, increases the number and activity of osteoclasts AntagonisticAntagonistic CT PTH .11Control of Bone DepositionControl of Bone ResorptionCa2+ controlled by negative feedback loop.12Promote the growth of new boneBring about the degeneration of cartilage cells.13Aging for skelet
5、al syetem happens when Osteoblast activity declines, while osteoclast activity remains level Loss of calcium from bones.14For female, this loss begins after age 40 but for male , this loss typically does not begin until after 60.15MENOPAUSE! Remember, estrogen(sex hormone for female) stimulates oste
6、oblast activity and synthesis of bone matrix Men continue to produce androgens (sex hormone for male) into late life and thus are not as affected.16Another effect for aging is the decrease in the rate of protein formation Less organic matrix more inorganic matrix Bones become brittle and easy to fra
7、cture.17When the loss of bone mass compromises normal function a person is diagnosed with osteoporosis.18Premature menopause Body build short women have less bone mass to begin withWeight thinner at greater riskSmoking decreases estrogen levelsLack of dietary calciumSedentary lifestyle decrease rate of absorptionDrugs alcohol, cortisone, tetracyclineNulliparity (never had children)Ancestry or Family history.19No smokingTake in more calciumDont sit all the dayBe careful when taking drugs.20