KINE 2P20 Lecture Notes - Lecture 12: Collagen, Bone Mineral, Amenorrhoea
9 May 2018
School
Department
Course
Professor
Nutrition 2P20
Calcium in Digestive Tract
- Absorbed by active transport and passive diffusion
▪ AT depends on Vit. D, increases synthesis of Ca transport protein
- ~25% of dietary calcium is absorbed
Regulation of Calcium***
- Powerful regulatory mechanism
▪ slight change triggers quick response
- Parathyroid hormone – raises Ca2+ when low
▪ released from bones
• stimulates reabsorption
▪ reduced excretion at kidney
▪ increase intestinal absorption (via Vit. D)
- Calcitonin – lowers Ca2+ when high
▪ Inhibits release from bones
• Stimulates formation
Calcium and Bone Health
- Bone: protein (collagen) and mineral (calcium)
- Maintain health bone: calcium, Vit. D, protein, Vit. K, P, Mg, F, Na, K
- Types of bone: cortical/compact (80%), trabecular/spongy (20%)
Bone Remodelling
- Bone is alive
- Continually broken down and reformed (remodelling)
▪ Cycles of reabsorption and formation
- Osteoblasts – bone forming cells
- Osteoclasts – bone reabsorbing cells
- Peak bone mass: maximum bone density achieved - ~16-30y/o
Osteoporosis
- Loss of bone, bone becomes more porous
- Silent disease until 50-60y/o
▪ Back pain, loss of height, fracture, hump
- Affects trabecular bone more (faster turnover rate)
▪ Regions with high Trabecular bone = fracture sites
• Wrist, femoral neck, vertebrae
- DXA measures bone mineral density ad content – assess risk by comparison to healthy
young adults
- Healthy trabecular bone is denser than trabecular bone weakened by osteoporosis
- Risk factors
▪ Depends on starting peak bone mass and the rate at which it is lost
▪ Age: loss starts ~35+, 0.3-0.5%/yr
▪ Sex 80% affected are women, lower peak, hormonal changes
• 5-7yr post-menopause
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Document Summary
Absorbed by active transport and passive diffusion: at depends on vit. Powerful regulatory mechanism: slight change triggers quick response. Parathyroid hormone raises ca2+ when low released from bones: stimulates reabsorption reduced excretion at kidney increase intestinal absorption (via vit. Types of bone: cortical/compact (80%), trabecular/spongy (20%) Continually broken down and reformed (remodelling: cycles of reabsorption and formation. Peak bone mass: maximum bone density achieved - ~16-30y/o. Silent disease until 50-60y/o: back pain, loss of height, fracture, hump. Affects trabecular bone more (faster turnover rate: regions with high trabecular bone = fracture sites. Dxa measures bone mineral density ad content assess risk by comparison to healthy: wrist, femoral neck, vertebrae young adults. Healthy trabecular bone is denser than trabecular bone weakened by osteoporosis. = lost in space: diet: inadequate intakes of protein, key vitamins and minerals. Prevention: achieve high peak bone mass when young and prevent loss.
