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Bone architecture
Bone is composed of compact and cancellous tissue. Compact tissue is dense like ivory while cancellous tissue is elastic and porous. Microscopically, bone is made up of lamellar and woven structures. Lamellar bone is strong with slow turnover found along lines of stress. Woven bone is immature and non stress-oriented found in embryonic skeletons. The periosteum encloses bone, supplying blood vessels in two layers. Bone marrow is yellow and fatty in adults but red and cellular in children. Bone is vascularized by nutrient arteries that branch throughout and emerge as veins in three locations.
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Bone architecture
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- 2. • Hardest structures •Toughness and elasticity Externally: Pink white Internally: Red • On section (1) Compact tissue-porous + dense like ivory (2) Cancellous tissue
- 3. MICROSCOPY SUBTYPE FEATURESEXAMPLE LAMELLAR Cortical (80%) Strong; slow turnover Along Lines Of Stress Femoral shaft Cancellous / Spongy >elastic; > turnover; < Young’s modulus Distal femoral epiphysis WOVEN Immature Non stress oriented Embryonic skeleton # callus Pathologic Weak, Flexible,High turnover, Osteosarcoma Fibrous dysplasia
- 5. Periosteum • Encloses bone •Supplies blood vessels • 2 layers (1)Outer-connective tissue+fat (2)Inner-elastic fibres forming a dense membranous network • Medullary membrane/ Internal periosteum
- 6. Periosteum In young • Thick •Vascular, • Loosely attached • Separated by soft tissue with osteoblasts • ossification on exterior of bone In adults • Thin • Less vascular • Closely attached • Osteoblasts converted to epitheloid layer. • Carry lymph from bone
- 7. • RAMIFICATION OFVESSELS • LIABILITY OF BONE EXFOLIATION OR NECROSIS.
- 8. BONE MARROW ADULT • yellowcolour • Long bones • Composition: 96% fat 1% areolar tissue + vessels 3 % fluid a. fibrous tissue b. blood vessels c. cells CHILD 1. Red colour 2. Short flat bones 3. Composition: 75% water 25% solid matter a. Cell globulin b. Nucleoproteid c. Extractives d. Salt e. Less fat
- 9. • TRUE “MARROWCELLS” OF KOLLIKER red marrow Majority of the cells Roundish nucleated cells smallest-erythroblasts
- 11. • GIANT CELLS-MYELOPLAQUES- OSTEOCLASTS morein red marrow large multinucleated protoplasmic mass ‘integrin’-attach TRAP + CA Fn: absorbtion of bone matrix Evacuate pits/cavities-”HOWSHIPS LACUNAE”
- 12. VESSELS • Compact bone-more numerous • Cancellous bone-less numerous larger size. Come through compact tissue • Largest and most numerous apertures for veins of cancellous tissue.
- 13. MEDULLARY / NUTRIENTARTERY High pressure system nutrient foramen; shaft accompanied by 1 or 2 veins branches in both directions to medullary membrane anastamoses with br. Of compact and cancellous tissue.
- 14. • METAPHYSEAL/EPIPHYEAL VESSELS Fromperiarticular vascular plexus- geniculate arteries • PERIOSTEAL SYSTEM Low pressure system
- 15. • Arterial flowin mature bone is centrifugal d/t high pressure endosteal system • In case of displaced fracture flow is reversed-becomes centripetal. • Arterial flow in immature bone-centripetal since periosteum is highly vascularised.
- 16. VEINS Emerge from 3places 1. Accompany artery 2. At the articular extremities. 3. Arising in compact tissue Venous flow in mature bone-centripetal Cortical vessels-venous sinusoids-emissary venous system.
- 17. LYMPHATICS 1. In periosteum 2.Within bone in Haversian system NERVES 1. Freely distributed in periosteum 2. Accompany nutrient vessels to interior 3. Most numerous in –articular extremities vertebrae larger flat bones
- 18. MINUTE ANATOMY Studied ontransverse section Haversian systems 1. Haversian canal 2. Lamallae 3. Lacunae 4. Canaliculi
- 20. Haversian Canal /Volkmanns Canal • // to long axis of bone • Branch + communicate • Average diameter: 1/500th of an inch • Larger near medullary cavity • Contains- 2 blood vessels delicate connective tissue nerve filaments lymphatics
- 21. LAMELLAE Primary / Fundamental/ Circumferential -medullary cavity of bone would be the HC Secondary / Special -Those laid down around actual HC Interstitial -between the various circular systems, filling the irregular intervals
- 22. LACUNAE branched bone cell/ corpuscle Processes of cell pass through canaliculi Fn: fluids for nutrition brought in contact with bone CANALICULI Do not communicate with the lacunae of neighboring HS.
- 23. CHEMICAL STRUCTURE • AnimalPart / Organic Part: 25% Bone Cells (4%) Matrix (20%) • Earthy / Inorganic Part 65% crystalline hydroxyappetite amorphous Ca2(PO4)3 Remainder: CaCO3, CaCl2 and MgSO4 Trapped ions: citrate, fluoride, Na K Mg
- 24. OSSIFICATION • Intramembranous skull, maxilla,mandible, clavicle mesenchymal tissue-scaffold for ossifn • Intracartilaginous • Ring of Lacroix-epiphsial ring formed. Does not further extend to epiphysis • Zone of Ranvier- ROL + lateral part of physis + mesenchymal cells
- 25. Ossification Centres • Shortbones: single point; in the centre • Long bone: central point for diaphysis (1st ) 1 or more for each extremity-epiphysis • Union of epiphysis with shaft occurs in reverse order to that in which ossification began (exception : fibula) • Regulated by direction of nutrient artery (knee-away ; elbow-towards)
- 26. • When 1epiphysis; medullary artery is directed towards it. • Eg: acromial end of clavicle distal end of the metacarpal bone of thumb and great toe proximal end of other metacarpals and metatarsals
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