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Metabolic Bone Diseases

Metabolic Bone Diseases. BY Dr. Abdullah H .A . Juma , FRCS Ed Associate Professor & Consultant Orthopaedic Surgeon. Introduction. Metabolic bone diseases describes a group of disorders due to abnormalities of formation ( bone morphology ) and metabolism of bone ( functions ) .

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Metabolic Bone Diseases

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  1. Metabolic Bone Diseases BY Dr. Abdullah H .A . Juma , FRCS Ed Associate Professor & Consultant Orthopaedic Surgeon

  2. Introduction • Metabolic bone diseases describes a group of disorders due to abnormalities of formation ( bone morphology ) and metabolism of bone ( functions ) . • Bone : An active tissue undergoing continuous structural & metabolic changes . The bone is surrounded by a bone fluid different from the whole body extracellular fluid .

  3. Bone characteristics • Bone Morphology . • Bone Functions .

  4. 1. Bone Morphology • Morphologically , bone can be mature (lamellar ) or immature ( woven ) or unmineralized ( osteoid ) . • 2 types of bone in mature skeleton : . . Compact cortical bone . Consists of 50% Haversian systems (osteons) & 50% interstitial bone . Osteons consist of rings of osteocytes around central canal which carries blood & lymph vessels . The cortical bone surrounds marrow cavities & form shafts of long bones . . . Cancellous bone . Anastomosing trabeculae within cortical bone and predominantly seen in vertebrae ,flat bones & ends of long bones .

  5. BoneMorphology • Organic matrix . • Bone cells . • Bone mineral . • Blood vessels . • Bone marrow .

  6. 1. Organic Matrix • It’s the frame work of bone . • 2 types : collagenous ( 90% ) and non– collagenous ( 10% ) . • Collagen is triple helix consist of 3 polypeptide alpha chains . Each chain has 1000 amino acids & synthesized within the fibroblasts or osteoblasts and is broken down by collagenases to hydroxyproline & hydroxylysine and excreted in urine .

  7. Collagen stability decreases with age. • 4 types of collagen . Type I only occurs in bone with low carbohydrate & < 10 hydroxylysine residues per alpha chain . • Non-collagenous is protein linked to substances forming proteoglycans & glycoproteins or exist as an isolated material such as Albumin & Alpha – Carboxyglutamic acid .

  8. Proteoglycans consist of a protein core linked to carbohydrate units such as mucopolysaccharides . • Glycoproteins .. 2 forms exist in the bone : . Sialoprotein . A high metal-binding capacity . . Alpha 2 heat-stable glycoprotein . Synthesized in liver .

  9. BoneMorphology • Organic matrix . • Bone cells . • Bone mineral . • Blood vessels . • Bone marrow .

  10. 2. Bone cells • Control formation , composition & resorption of bone . • Types of cells : . Osteoblasts . . Osteoclasts . . Osteocytes . . Fibroblasts . . Myeloproliferative cells .

  11. Osteoblasts • Bone forming cells , synthesizing collagen , non-collagen & mineralization of bone . • Uniform in size . • Mononuclear & basophilic cytoplasm. • Lie in single layers close to the osteoid tissue of newly formed bone. • High content of Alkaline Phosphatase . • Have fine processes which extend into the osteoid tissues . • If resting , appear spindle & flat . • If active , appear larger & plump .

  12. 2. Bone cells • Types of cells : . Osteoblasts . . Osteoclasts . . Osteocytes . . Fibroblasts . . Myeloproliferative cells .

  13. Osteoclasts

  14. Metabolic bone diseases are caused by an imbalance in the metabolism of bone resorption & deposition due to : • Defect of Mineralization . • Defect of bone matrix . • Excessive bone resorption . • Paget’s disease .

  15. Defect of Mineralization . • Defect of bone matrix . • Excessive bone resorption . • Paget’s disease .

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