metabolic bone diseases by dr. abdullah h.a. juma, frcs ed associate professor & consultant...
TRANSCRIPT
Metabolic Bone Metabolic Bone DiseasesDiseases
BYBYDr. Abdullah H .A . Juma , FRCS Dr. Abdullah H .A . Juma , FRCS
EdEdAssociate Professor & Associate Professor &
Consultant Orthopaedic Consultant Orthopaedic SurgeonSurgeon
IntroductionIntroduction
Metabolic bone 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 .
Bone characteristics
1. Bone Morphology .
2. Bone Functions .
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 .
Bone Morphology
1. Organic matrix .2. Bone cells .3. Bone mineral .4. Blood vessels .5. Bone marrow .
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 .
Collagen stability decreases with Collagen stability decreases with age.age.
4 types of collagen . Type I only 4 types of collagen . Type I only occurs in bone with low occurs in bone with low carbohydrate & < 10 hydroxylysine carbohydrate & < 10 hydroxylysine residues per alpha chain .residues per alpha chain .
Non-collagenous is protein linked to Non-collagenous is protein linked to substances forming proteoglycans substances forming proteoglycans & glycoproteins or exist as an & glycoproteins or exist as an isolated material such as Albumin & isolated material such as Albumin & Alpha Alpha –– Carboxyglutamic acid . Carboxyglutamic acid .
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 .
Bone Morphology
1. Organic matrix .2. Bone cells .3. Bone mineral .4. Blood vessels .5. Bone marrow .
22 . .Bone cells
Control formation , composition & resorption of bone .
Types of cells : . Osteoblasts . . Osteoclasts . . Osteocytes . . Fibroblasts . . Myeloproliferative cells .
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 .
22 . .Bone cells
Types of cells :
. Osteoblasts . . Osteoclasts . . Osteocytes . . Fibroblasts . . Myeloproliferative cells .
Osteoclasts
Metabolic bone diseases are Metabolic bone diseases are caused by an imbalance in the caused by an imbalance in the
metabolism of bone resorption & metabolism of bone resorption & deposition due todeposition due to: :
1.1. Defect of Mineralization .Defect of Mineralization .
2.2. Defect of bone matrix .Defect of bone matrix .
3.3. Excessive bone resorption .Excessive bone resorption .
4.4. PagetPaget’’s disease .s disease .
1.1. Defect of Mineralization .Defect of Mineralization .
2.2. Defect of bone matrix .Defect of bone matrix .
3.3. Excessive bone resorption .Excessive bone resorption .
4.4. PagetPaget’’s disease .s disease .