1. BONE
Dr Laxman Khanal
MS- Human Anatomy
Batch-2011
Date-25-04-2012
2. OBJECTIVESâŚ.
⢠Introduction
⢠Functions.
⢠Embryological source of bone.
⢠Parts of bones
⢠Laws of ossification
⢠Blood supply of bones
⢠Classification of bones
25/27/2012 1212413114 2
3. âŚOBJECTIVES
⢠Microscopic study of bones.
ďCompact and cancellous bone
⢠Composition of bones.
⢠Ossification of bones.
ď Intramembranous
ď Endochondral
⢠Growth of bones
⢠Factors affecting the bone
25/27/2012 1212413114 3
4. Introduction
⢠Bone is mineralized dense connective tissue
⢠Made up of few cells in mineralized matrix
⢠Consists of 30-40 % of our body weight.
⢠Dynamic in nature
25/27/2012 1212413114 4
5. Function
⢠Framework of the body.
⢠Attachment of muscle and tendon.
⢠Permit the movements in body parts.
⢠Protection of organs.
⢠Haematopoiesis
⢠Reservoir of minerals and fat.
25/27/2012 1212413114 5
6. Embryological source
⢠Embryonic mesodermal cells
⢠Neural crest cells
Primodial for the different types of cells.
25/27/2012 1212413114 6
8. Parts of bones
⢠Epiphysis â secondary centers
ďPressure epiphysis
ďTraction epiphysis
ďAtavistic epiphysis
⢠Diaphysis â primary center
ďStrongest part of bone
25/27/2012 1212413114 8
10. ⢠Metaphysis- epiphysial ends of a diaphysis
ďMaximum blood supply
⢠Epiphysial plate of cartilage- separate
epiphysis from metaphysis.
ďMaximum growth
25/27/2012 1212413114 10
11. â˘Medullary cavity
medullary cavity
⢠filled with yellow marrow in adults
⢠lined with endosteum
25/27/2012 1212413114 11
12. Principles of Ossification
⢠Primary ossification center âbefore birth
⢠Secondary ossification center- after birth
⢠Ossification center which appears first is
usually last to fuse except for Fibula.
⢠In long bone with single epiphysis, that
epiphysis is at the movable end
25/27/2012 1212413114 12
13. Principles of ossification
⢠Larger the epiphysis earlier the ossification
center appears in long bone
⢠If epiphysis develops from more than one
centers the various centers coalesce before
union occurs with the diaphysis.
⢠When epiphysis fuses with the diaphysis the
growth ceases.
⢠This fusion occurs 1 year earlier in females
than in males.
25/27/2012 1212413114 13
14. Blood supply
⢠Nutrient artery
ďterminates in the adult metaphysis by
anastomosing with epiphysial, metaphysial
and periosteal arteries.
ďSupplies medullary cavity , inner 2/3rd of
cortex and metaphysis.
⢠Periosteal arteries
ďEnter the Volkmannâs canals . Supply outer
1/3rd of cortex.
25/27/2012 1212413114 14
16. ⢠Epiphysial arteries
ďDerived from periarticular vascular
arcades(circulus vasculosus) found on the
nonarticula bony surface.
⢠Metaphysial arteries
ďDerived from the neighbouring systemic
vessels.
25/27/2012 1212413114 16
26. Compact and Spongy Bone
⢠Compact bone located where stresses are
limited in direction.
⢠Spongy bone located where stresses are
weaker or multi-directional.
25/27/2012 1212413114 26
27. Periosteum and endosteum
⢠Periosteum
ďSuperficial surface of all bone except in joint
cavities.
ďProvide route for blood and nerve supply
ďParticipate in bone growth and repair
ďOuter fibrous layer and inner cellular layer
ď perforating fibers called as Sharpeyâs fibers
25/27/2012 1212413114 27
29. ⢠Endosteum
ďLines the marrow cavity
ďIncomplete cellular layer
ďWhere layer is incomplete, Osteoblasts and
osteoclasts can deposit or remove matrix
components.
ďShallow groove formed by osteoclasts called
as Howshipâs lacunae
25/27/2012 1212413114 29
31. Composition of Bone
⢠cellular structures in ground substance
⢠Ground substance made up of
ďInorganic minerals and organic matrix
⢠Organic matrix(35%)
ďCollagen type 1
ďGlycosaminoglycans
ďProteoglycans, osteonectin and osteocalcin
25/27/2012 1212413114 31
32. ⢠Inorganic content(65%)
ď largely made up of Ca ++ , PO4--- and OH- .
⢠These ions arranged parallel to the direction
of collagen fibers by forming a crystalline
structure called as Hydroxyapatite .
Ca10(Po4)6(OH)2
ďLiving bone contain 20% of water
25/27/2012 1212413114 32
33. ⢠Inorganic content give rigidity to the bone
⢠Organic content give the elasticity to the
bone.
⢠Lack of inorganic content- soft bone
⢠Lack of organic content- brittle bone
25/27/2012 1212413114 33
34. Intramembranous osteogenesis
⢠Bone formation directly from the
mesenchymal sheath( formed by collagen
fibers in between the mesenchymal cells)
⢠Not the common process
⢠Also called as dermal ossification because of
its presence in deeper layers of dermis.
⢠Roofing bones of skull, clavicle and mandible.
25/27/2012 1212413114 34
35. Intramembranous ossification
⢠Mesenchymal cells condensation
⢠Secretion of organic matrix by the
mesenchymal cells which consists of collagen
fibers. Thus forming the mesenchymal sheath.
⢠Localized differentiation of osteoblasts with in
sheath
25/27/2012 1212413114 35
36. ⢠Bone grows outward from the ossification
center in radiating fashion and forms
tabeculae.
⢠Trapped osteoblast in between the layer of
bone is called as osteocytes.
⢠Blood vessels grows and trapped in between
trabeculae.
⢠Initially spongy bone is formed which later
changed to the compact bone.
25/27/2012 1212413114 36
37. Endochondral ossification
⢠Most bone formed by this way
⢠Cartilaginous model is replaced(!!) by the
bone.
⢠Chondrocyte hypertrophy
⢠Degeneration and calcification
⢠Vascular invasion
⢠ossificaton
25/27/2012 1212413114 37
40. Growth at epiphysial plate
⢠Zone of resting cells
⢠Zone of proliferating
cells
⢠Zone of hypertrophic
cells
⢠Zone of calcified cells
ďśIncrease in length
25/27/2012 1212413114 40
42. ⢠Bone is the dynamic tissue so its composition
varies according to the regulating factors.
⢠99% of body calcium, 80% of phosphorus and
65% of sodium and magnesium is reserved in
the bone
⢠Calcium is needed for many physiological
function so it is tightly regulated at normal
level (9-11mg/dl)
25/27/2012 1212413114 42
44. Clinical Aspects
⢠Subluxation
ďIncomplete or partial displacement of joint
⢠Dislocation / Luxation
ďComplete displacement of joint
⢠Fracture
ďLoss of continuity of bone due to abnormal
forces or due to weakening of bone.
25/27/2012 1212413114 44
45. ⢠Types of fractures
ďSimple or Closed
ďCompound or Open
ďComminuted
ďGreenstick
⢠Not complete
⢠Common in children.
25/27/2012 1212413114 45
48. Bone disorders
⢠Osteopenia
ďDecreased in bone mineral density(BMD)
⢠Osteoporosis
ďLoss of both bone salts and collagen content
⢠Osteomalacia/ Rickets
ďLoss of mineral content but not the collagen
25/27/2012 1212413114 48
49. Bone disorders
⢠Pagetâs disease
ďAbnormal bone remodeling , lead to abnormal
thickening of the bone
ďConsequences ???
⢠Osteomyelitis
ďInflammation of bone marrow
ďMost commonly by staphylococcus aureus
25/27/2012 1212413114 49
50. Bone disorders
⢠Osteogenic sarcoma (osteosarcoma)
ďBone cancer that affects osteoblast
25/27/2012 1212413114 50