This document provides an overview of bone anatomy, histology, and blood supply. It discusses that bone is a dynamic connective tissue composed of an organic matrix and inorganic minerals. It describes the cellular components of bone including osteoblasts, osteoclasts, and osteocytes which are responsible for bone formation, resorption, and remodeling. The document outlines the classification of bones and explains the structure of long bones including the diaphysis, metaphysis, and epiphysis. It provides details on cortical and cancellous bone, woven and lamellar bone, and the microstructure of compact and spongy bone.

1. Topic:- BONE ANATOMY-
Histology & Blood Supply
MODERATOR- Dr. PANDURANGA
PRESENTER- Dr. KARTHIK M V

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)

5. • The organic matrix gives bone its form and provides its tensile
strength
• The inorganic component gives compressive strength.

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.

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.

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

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.

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

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

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”

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

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

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

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.

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

84. THANK YOU