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8 Cards in this Set

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Describe the dietary factors that influence bone.
• Minerals:
• calcium and phosphorus (also magnesium, fluoride and manganese)
• Vitamins:
• Vitamin A → stimulates activity of osteoblasts
• Vitamin C →needed for collagen synthesis
• Vitamin D → stimulates calcium absorption
• Vitamins K, B12 → needed for synthesis of bone proteins
Describe the roles of calcitonin and parathyroid hormone in the regulation of blood calcium.
• Calcitonin- hormone involved in calcium homeostasis
• Stimulus: high blood calcium
• Source: thyroid gland (parafollicular cells)
• Target tissue: bone, kidney, intestine
• Actions (goal is to decrease blood Ca):
• Inhibits osteoclast activity (decreased bone resorption)
• Increases excretion of calcium at kidney
• Inhibits absorption of calcium at intestine
End result: decrease blood calcium

• Parathyroid Hormone- hormone involved in calcium homeostasis
• Stimulus: low blood calcium
• Source: parathyroid gland
• Target tissues: bone, kidney, intestine
• Actions (goal is to increase calcium):
• Stimulates osteoclast activity (increased bone resorption)
• Decreases excretion of calcium at kidney
• Stimulates intestinal absorption of calcium and promotes calcitriol (Vit. D) action
End result: increase blood calcium
Describe the vitamin D pathway, and the role of calcitriol in calcium homeostasis.
Vitamin D Pathway:

• Calcitriol: active form of vitamin D
• 1, 25 dihydroxycholecalciferol or
• 1, 25 dihydroxy vitamin D3
• Vitamin D is a steroid hormone – derived from cholesterol (lipophillic / hydrophobic)
• Stimulates osteoclast activity (increases bone resorption)
• Decreases calcium excretion at the kidney
• Increases calcium absorption at the intestine (works well with PTH to stimulate absorption)
End result: increase blood calcium
Describe the role of dietary calcium in maintenance of bone mass and know the recommended allowance for calcium intake for young adults.
• How much calcium should you have per day?
• Young adults (19-50 years old) need 1000mg calcium from diet and supplements to avoid bone loss
• Maintaining calcium in blood is priority
• 8.5-11.0→ this is maintained even when we have too much or too little (unless tumor affects this)
Describe how exercise can affect bone mass.
Role of exercise
Goal: reach the fracture threshold later in life
• Exercise early in life – increase peak bone mass
• Exercise later in life – prevent bone loss
Other benefits of exercise – fall prevention
– Improved strength
– Improved balance and coordination
Describe the role of growth hormone, thyroxine and sex hormones in modulating bone mass.
?
Describe the skeletal disorders that arise from abnormal levels of human growthhormone.
?
Define osteoporosis and identify the risk factors for development of the disease. Offer strategies for prevention of osteoporosis.
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