Bone architecture

BONE ARCHITECTURE

Dnyanesh Lad

• Hardest structures• Toughness and elasticity Externally: Pink white Internally: Red• On section (1) Compact tissue-porous + dense like ivory (2) Cancellous tissue

MICROSCOPY SUBTYPE FEATURES EXAMPLE

LAMELLAR Cortical (80%)

Strong; slow turnoverAlong 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, Random

OsteosarcomaFibrous dysplasia

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

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

• RAMIFICATION OF VESSELS

• LIABILITY OF BONE EXFOLIATION OR NECROSIS.

BONE MARROW ADULT • yellow colour• Long bones• Composition: 96% fat 1% areolar tissue +

vessels 3 % fluida. fibrous tissueb. blood vesselsc. cells

CHILD1. Red colour2. Short flat bones3. Composition: 75% water 25% solid mattera. Cell globulinb. Nucleoproteidc. Extractivesd. Salte. Less fat

• TRUE “MARROW CELLS” OF KOLLIKER

red marrow Majority of the cells Roundish nucleated cells smallest-erythroblasts

• GIANT CELLS-MYELOPLAQUES- OSTEOCLASTS more in red marrow large multinucleated protoplasmic mass‘integrin’-attachTRAP + CA

Fn: absorbtion of bone matrix Evacuate pits/cavities-”HOWSHIPS LACUNAE”

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.

MEDULLARY / NUTRIENT ARTERY

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.

• METAPHYSEAL/EPIPHYEAL VESSELS From periarticular vascular plexus-

geniculate arteries

• PERIOSTEAL SYSTEM Low pressure system

• Arterial flow in 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.

VEINSEmerge from 3 places1. Accompany artery2. At the articular extremities.3. Arising in compact tissue

Venous flow in mature bone-centripetal

Cortical vessels-venous sinusoids-emissary venous system.

LYMPHATICS1. In periosteum2. Within bone in Haversian system

NERVES1. Freely distributed in periosteum2. Accompany nutrient vessels to interior3. Most numerous in –articular extremities vertebrae larger flat bones

MINUTE ANATOMY

Studied on transverse section Haversian systems1. Haversian canal 2. Lamallae 3. Lacunae4. Canaliculi

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

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

LACUNAEbranched bone cell / corpuscleProcesses of cell pass through

canaliculiFn: fluids for nutrition brought in

contact with bone CANALICULI Do not communicate with the lacunae

of neighboring HS.

CHEMICAL STRUCTURE• Animal Part / 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

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

Ossification Centres

• Short bones: 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)

• When 1 epiphysis; 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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