2. • Bone is a specialized dense connective tissue
• Consisting of organic matrix, inorganic minerals, cells and water.
• It is a mesodermal in origin.
• Bone is Dynamic tissue that undergoes continuous remodeling
throughout life
3. BONE ( OSTEON)
ORGANIC/ OSTEOID (40%) INORGANIC (60%)
CELLS PROTEIN MATRIX
OSTEOBLAST OSTEOCLAST OSTEOCYTES
(Hydroxyapatite)
4.
5. • The organic matrix gives bone its form and provides its tensile
strength
• The inorganic component gives compressive strength.
6.
7. INORGANIC MATRIX
They are responsible for mineralization of bone
Reservoir for minerals
The bone matrix contains about 99% of the body’s calcium,
80% of the phosphate
8. PROTEIN MATRIX
• Collagen is principle protein of bone
• Bone contains abundant of Type 1 Collagen (90%)
• Synthesised by Osteoblasts
• Type 1 collagen also seen in skin, vessels, Meniscus, sclera
9. • For example, osteogenesis
imperfecta have
abnormality in synthesis and
processing of Type 1
collagen
• Increase bone fragility
(Brittle Bones)
10. • Other Non Collagenous protein are
1. Osteopontin
2. Osteonectin
3. Osteocalcin
Functions of protein matrix
• Help in Mineralization of bone
• Support osteoblast in survival, maturation and development.
11. Cellular components of Bone
1. OSTEOBLAST :- Bone formation
2. OSTEOCLAST :- Bone resorption
3. OSTEOCYTES :- Mature / Resting Osteoblast
The combined action of Bone formation and Bone resorption contributes
to Bone Remodelling
ORIGIN :- 1. Mesenchymal stem cells – Osteoblast & Osteocytes
2. Osteoclasts are related to macrophages
12. Osteoprogenitor Cells
- Pluripotent stem cells
- Mesenchymal in origin
- Found in periosteum ( deepest layer ) & Endosteum
- Osteogenic potential
13. OSTEOBLAST
• Derived from Osteoprogenitor cells
• They are 15-20 um, basophilic cuboidal mononuclear
cells
• Found on the surface of growing bone by forming
monolayer
• They are responsible for synthesis of osteoid bone
matrix.
• Osteoblast are rich in ALP
14. Other functions
1. Production of Non collagenous proteins ( osteocalcin, osteonectin )
2. Regulation of bone metabolism
3. Differentiation of Osteoclasts.
15. • osteoblast secrete RANK Ligand to regulate the activation and
differentiation of Osteoclasts that then affect remodelling
• Denosumab is a drug which inhibits RANK ligand and prevent bone
resorption
• Used in Osteoporosis
16. OSTEOCYTES
• Contribute more than 90% of cells of mature skeleton
• Oval / lens shaped
• Derived from osteoblast, which have ceased matrix formation
• They have long cytoplasmic processes
• The spaces they occupy is known as Lacunae
• They are connected to surface osteoblast by network of
canaliculi
17. OSTEOCLAST
• Multinucleated cells related to macrophages.
• Found at bone remodelling site.
• Least in number
• Ruffled border
• Acidophilic
• Resorption of bone
• Stimulators- PTH, osteoblast, decreased serum calcium
• Cells are found in pits – Resorption bays/ Lacunae of Howship.
18.
19. Control of Bone Cell Activity
• Throughout life, osteoclasts remove bone matrix and osteoblasts replace
it
• Repetitive loading of the skeleton can increase bone formation relative to
bone resorption and thereby increase bone mass and strength.
• Immobilization decreases bone formation relative to bone resorption,
thereby decreasing bone mass and strength
20. • Factors
1. Nutrition- protein, Vit D deficiency
2. Exercise
3. Hormones- PTH, Thyroid,
4. Corticosteroids- reduces synthesis activity of Osteoblasts
21. WOLFF’s LAW – remodeling occurs in response to Mechanical stress
• 1. Increasing mechanical stress increases bone gain
• 2. Removing external mechanical stress increases bone loss which is
reversible (to varying degrees) on remobilization
22. • SKELETAL ORGANIZATION
• Typically there are about 206 bones
• For convenience the skeleton is divided into the:
Axial skeleton
Appendicular skeleton
• DIVISION OF SKELETON
• Axial Skeleton
• Skull
• Spine
• Rib cage
• Appendicular Skeleton
• Upper limbs
• Lower limbs
• Shoulder girdle
• Pelvic girdle
23. CLASSIFICATION OF BONES
• LONG BONES
• SHORT BONES
• FLAT BONES
• IRREGULAR BONE
• PNEUMATIC BONES
• SESAMOID BONES
24. LONG BONES
EPIPHYSIS- Expanded ends
DIAPHYSIS- Shaft
Shaft- Borders, surfaces, medullary cavity.
Further divided into:
a. Typical Long Bones
b. Miniature Long Bones
c. Modified long bone
25. a. Typical long Bones:-
contains two epiphysis
Ex: Humerus, Radius, Femur, Tibia
b. Miniature long bones:-
contains only one epiphysis
Ex: Metacarpals, Phalanges
26. c. Modified Long Bones:-
Horizontally placed
No medullary cavity
Ossifies by membrane
Clavicle
27. • SHORT BONES:-
Named according to their shapes
Ex: Cuboid (like a cube), Scaphoid (boat shaped)
• FLAT BONES:-
Form boundaries of certain bodycavities
protective in function
Ex:- Bones in vault of skull,sternum, ribs and scapula
28. • PNEUMATIC BONES
Certain irregular bones contain large air spaces lined by epithelium
Make the skull light in weight, help in resonance of voice
Ex – maxilla, sphenoid, ethmoid, etc.
• IRREGULAR BONES:-
Have complex shapes
Ex- Hip bone, Vertebrae
29. • SESAMOID BONES
Bony nodules found embedded in the tendons or joint capsules
No periosteum and ossify after birth
Bones which develop in tendon of muscle
• FUNCTIONS OF SESAMOID BONES
(a) to resist pressure
(b) to minimize friction
30. Ex – patella -- quadriceps femoris
pisiform– Flexor carpi ulnaris
fabella– lateral head of gastrocnemius
31. PARTS OF LONG BONE
• EPIPHYSIS
• METAPHYSIS
• DIAPHYSIS
32. EPIPHYSIS
• The ends of a long bone which ossify from secondary centers are
called epiphyses.
• Lies B/W Physis & Articular cartilage
• Usually Intra articular (joint formation)
• The periosteum in intra articular layer lacks Cambium layer that has
totipotent cell rests.
33. • Types of Epiphysis
1. Pressure epiphysis – transmission of the weight.
Ex-head of femur
2. Traction epiphysis – provides attachment to tendons which exerts a
traction on the epiphysis. Ex- trochanters of femur.
3. Atavistic epiphysis – phylogenetically an independent bone, which
fuses to another bone. Ex-coracoid process of scapula.
4. Aberrant epiphysis – not always present. Ex- head of the 1st
metacarpal and base of other metacarpal.
34.
35. METAPHYSIS
The epiphysial ends of a diaphysis are called metaphysis.
It contains more Cancellous bone
Blood vessels arranged “Hair pin Loop”
Vascular stasis
Less defence cells
“metaphysis more susceptible to Osteomyelitis”
Any Fractures--- good blood supply– healing is good
36. DIAPHYSIS
It ossifies by Primary Ossification Centre
Made of thick Cortical Bone
Filled with Bone Marrow
Note:-
• Metaphyseal Fractures- always unites ( may go into Malunion)
• Epiphyseal fractures- Destruction of articular cartilage (osteoarthritis)
• Diaphyseal fractures- Non Union
37. • MEDULLARY CAVITY
Lined by Endosteum
Filled with red or yellow bone marrow
1. Red – at birth – hemopoiesis
2. Yellow – as age advance – atrophies – fatty
3. Red marrow persists in the cancellous ends of long bones, Vertebrae
38. • PHYSIS LAYERS
Reserve Zone :- cells store lipids, glycogen
Proliferative Zone :- proliferation of Chondrocytes
Hypertrophic Zone :- a) Maturation zone
b) Degenerative zone
c) zone of provisional Calcification
Primary Spongiosa
Secondary Spongiosa
39.
40. 1. Gaucher’s Disease --- Resting zone
2. Achondroplasia --- Proliferative zone
3. SCFE --- Hypertrophic zone
4. Rickets --- Hypertrophic zone ( zone of provisional calcification)
41. PERIOSTEUM
Outer Fibrous layer
Inner Cellular layer ( cambium layer) contain Osteoprogenitor cells & osteoblast --
-- new bone
Absent at articular surfaces and sesamoid bones
Periosteum is anchored to bone by SHARPEY’S FIBRES
Rich in blood supply- periosteal vessels
42. • PERIOSTEUM - FUNCTIONS
muscles, tendons and ligaments attachment
Forms a nutritive function ( blood supply to outer
1/3rd of cortex of bone via periosteal vessels).
Can form new bone when required.
Forms a limiting membrane.
43. ENDOSTEUM
Lines the walls of Bone cavities including marrow spaces
The osteoprogenitor cells present in endosteum and periosteum is responsible
for thickness of bone.
44.
45. Structural classification
1. Cortical bone/ Compact bone
Provide mechanical strength
Predominantly found in diaphyseal region
Provides attachment to tendons, ligaments and periosteum
Metabolically less active
Usually minimal change in osteoporosis
46. 2. Cancellous bone/ spongy/ Trabecular bone
Predominantly seen in metaphyseal and epiphyseal regions.
more metabolically active than cortical bone.
Preferred in bone grafting for higher osteogenic potential.
Undergoes great amount of resorption in osteoporosis
47.
48. • Microscopic Classification
(based on collagen fibres arrangement)
1. Woven bone
immature bone
randomly arranged collagen fibres in interlacing fashion
more cellular
seen in fetus, callus, pathological (osteosarcoma)
synthesis triggered by PDGF & IGF
It is more flexible, more easily deformed, and weaker than mature lamellar bone
49. 2. Lamellar bone
Mature bone
Well organized collagen fibres (parallel bundles)
It is more strong , rigid, cannot be easily deformed
50. HISTOLOGY
Lamella is a thin plate of bone made up of ground substance with
collagen fibres and mineral salts
The collagen fibres in one lamella run parallel to each other
b/w each layers there are flat spaces called Lacunae
Osteocytes are trapped in Lacunae
Osteocytes are interconnected by canaliculi
51.
52.
53. SPONGY BONE
made of meshwork of bony plates called Trabeculae
Trabeculae are Branching, anastomosing
Contain Lamellae, with Lacunae
Contain spaces filled with haematopoietic tissue/ bone marrow
Trabeculae are covered by Endosteum
“No Haversian System”
54.
55.
56.
57. COMPACT BONE
Contains 3 types of Lamellae
1. Circumferential lamellae ( outer & inner)
2. Concentric Lamellae
3. Interstitial Lamellae
Outer Circumferential- just inside periosteum
Inner Circumferential- Just inside endosteum
Concentric around Haversian systems
Interstitial- b/w Haversian systems
58.
59.
60. The structural and functional unit of compact bone is Osteon/
Haversian system
Central haversian canal contains nerve fibres, blood vessels
b/w lamellae are lacunae with Canaliculi
Lacunae contains osteocytes
“ VOLKMAN’S CANAL’ connects one haversian canal to another
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71. The primary centres appear before birth, usually during 8th week of
intrauterine life;
secondary centres appear after birth
A primary centre forms diaphysis.
secondary centres form epiphyses.
Fusion of epiphyses with the diaphysis starts at puberty and is
complete by the age of 25 years,
After which no more bone growth can take place
72. The law of ossification states that secondary centres of ossification
which appear first are last to unite.
The end of a long bone where epiphysial fusion is delayed is called
the growing end of the bone.
73. BLOOD SUPPLY OF BONE
• Bone receives 5-10% of cardiac output
• LONG BONES – derived from
• 1. Nutrient artery
• 2. Periosteal artery
• 3. Epiphyseal artery
• 4. Metaphyseal artery
74. • Nutrient artery
Enters through the nutrient foramen
Divides into ascending and descending branches gives radial
branches in the medullary cavity
Branch divides – small spiral branches
terminate in adult metaphysis
Anastomosing with the epiphysial, metaphyseal and periosteal
arteries
Supplies the medullary cavity , inner 2/3 of the cortex and
metaphysis
75. • The nutrient foramen is directed away from the
growing end of the bone
• 'To the elbow I go, from the knee I flee’
• The growing ends of bones in
upper limb are upper end of humerus and
lower ends of radius and ulna.
In lower limb, the lower end of femur and
upper end of tibia.
76. • Periosteal arteries
- Enter the volkmann’s canals to supply the outer 1/3 of the cortex
• Metaphyseal arteries
- They are derived from neighbouring systemic vessels
- They anastomosis with spiral branches of nutrient artery
- Metaphysis more vascular
• Epiphyseal artery
-They are derived from periarticular vascular arcades
77.
78. • Blood supply of Short Long bones
They have single epiphysis and single metaphysis
The nutrient artery entering the shaft divides into plexus immediately
Chief reason for TB & Syphilis (dactylitis) in middle of shaft
More common in early years
After growth ceased periosteal vessels dominate
Other end periosteal vessels assist supply.
79. • FLAT BONES
Nutrient vessel enter breaks up into branches which ramify all over
the bone.
Periosteal supply is profuse.
80.
81. Direction Of Blood flow
• Mature Bone
- Centrifugal ( inside to outside)
- High pressure nutrient to low pressure periosteal system
• Immature Bone
- Centripetal ( outside to inside)
- Low periosteal pressure predominates
82. Fractures
a) Immediate phase:-
initially decrease in blood flow
flow is Centripetal (outside to inside)
b) Hours to days:-
Blood flow increases
Peaks at 2 weeks, returns to normal in 3-5months
83. REFERENCE’S
1. CAMPBELL’S OPERATIVE ORTHOPAEDICS
2. NETTER’S CONCISE ORTHOPAEDIC ANATOMY
3. SYNOPSIS OF SURGICAL ANATOMY, Lee McGregor
4. DIFIORE’S ATLAS OF HISTOLOGY WITH FUNCTIONAL CORRELATIONS
5. GRAY’S ATLAS OF ANATOMY
6. TUREK’S ORTHOPAEDICS- PRINCIPLES AND THEIR APPLICATION
7. ESSENTIAL ORTHOPAEDICS PRINCIPLES & PRACTICE, MANISH VARSHNEY