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Bone Diseases and Abnormalities. Jake Turner and Roger Deering. Learning Objectives. Explain how the structure of bone allows it to carry out its functions; (strong due to hydroxyapatite crystals, flexible due to collagen, good loadbearing due to honeycomb structure)
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Bone Diseases and Abnormalities Jake Turner and Roger Deering
Learning Objectives • Explain how the structure of bone allows it to carry out its functions; (strong due to hydroxyapatite crystals, flexible due to collagen, good loadbearing due to honeycomb structure) • Compare the structure and function of cortical and trabecular bone; (Cortical = Strong, trabecular = weak, but quick to make) • Describe the importance of bone quality in addition to bone mineral content in overall bone strength; (if the structure is poor, the bone will be weak no matter what) • Describe the principles of osteoporosis prevention and management; (oestrogen, bisphosphonates, weight bearing, don’t give drugs that weaken bone) • Explain the physiological basis of the pharmacological management of osteoporosis; (keep calcium in the bone, ensure that osteoblast activity is at least equal to osteoclast activity) • Outline the mechanisms of action of drugs used to treat osteoporosis; (Calcium regulation, osteoblast / osteoclast regulation) • Give examples of common abnormalities of bone and explain the physiological basis of their development. (Rickets, osteoporosis, osteopenia, Paget’s disease of the bone, hyperparathyroidism)
Functions of bone • Loadbearing • Haematopoiesis • Protection • Mineral buffer • Movement • Hearing • Acid base balance • Fat storage
Rickets and Osteomalacia • Rickets is ONLY in children • Both cause softening of the bones, and abnormal bone growth. • Causes • Insufficient nutritional quantities or faulty metabolism of vitamin D or phosphorus • Renal tubular acidosis • Malnutrition during pregnancy • Malabsorption syndrome • Hypophosphatemia • Chronic renal failure • Tumour-induced osteomalacia • Long-term anticonvulsant therapy • Coeliac disease • Cadmium poisoning, Itai-itai disease
Rickets and Osteomalacia • Rickets is ONLY in children • Both cause softening of the bones, and abnormal bone growth. Causes Vitamin D deficiency! Signs and symptoms: Weak bones Bone pain Muscle weakness Hypocalcaemia Compressed vertebrae Pelvic flattening Easy fracturing Bone softening Bending of bones
Hyperparathyroidism • The function of parathyroid hormone is to increase blood calcium levels. • This leads to weak bones, and possible calcium toxicity • Primary, secondary and tertiary
Osteoporosis and osteopenia • Diagnosed by: • DEXA scans (Dual Energy X-ray Absorbitometry) • If the bone density is more than 1 standard deviation from the average bone density of a 25 year old of the same gender then the diagnosis is osteopenia • If the bone density is 2 or more standard deviations below the average bone density of a 25 year old of the same gender then the diagnosis is osteoporosis