Bone is a mineralized connective tissue that forms the endoskeleton of vertebrates. It has both compact and spongy structures and develops through either membranous or endochondral ossification. Bone is made up of osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts. Osteoblasts form new bone tissue while osteoclasts resorb old or damaged bone. The intricate blood supply through nutrient arteries is essential for bone growth and healing. Fractures heal through the formation of a hematoma, fibrocartilaginous callus, bony callus, and remodeling into secondary bone.

1. BONE STRUCTURE AND ITS CLINICAL
I M P O R T A N C E
Dr GIRIDHAR
BOYAPATI
P.G

2. What is Bone? – Mineralized connective
tissue
- constitute part of the endoskeleton of vertebrates

3. Classification
REGION- Axial, Appendicular
SHAPE - Long bones, short bones, irregular, pneumatic,
sesamoid, accessory
STRUCTURE
Macroscopic – Compact
Spongy
Microscopic – Lamellar (Secondary Bone)
Woven/fibrous(Primary Bone)
DEVELOPMENT – Membranous
Cartilaginous
Membrano-cartilaginous

4. ENDOCHONDRAL OSSIFICATION
MESENCHYMAL CELLS
CHONDROBLASTS
CHONDROCYTES
CARTILAGE MODEL OF FUTURE BONE
OSTEOBLASTS

5. Endochondral Ossification

6. Endochondral Ossification

7. Endochondral Ossification Defects –
AD Inheritance
• Achondroplasia
• Thanatophoric Dysplasia
• Hypochondroplasia
Mutation in FGFR 3 gene

8. Intramembranous Ossification

9. EXAMPLES OF INTRAMEMBRANOUS
OSSIFICATION
1. EMBRYONIC FLAT BONES :
SKULL, PELVIS, MAXILLA, MANDIBLE, CLAVICLE
2. DISTRACTION OSTEOGENESIS
3. FRACTURE HEALING WITH RIGID FIXATION
4.BLASTEM BONE

10. PERIOSTEAL OSSIFICATION
OSTEOGENIC CELLS FROM PERIOSTEUM
LAY PARLLEL LAYERS OF COMPACT BONE

11. Bone cells
Osteo progenitors
(Pleuripotent stem
cells)
Osteoblasts
("bone makers")
Osteocytes
("bone cells")
Osteoclasts
(“bone breakers”)
remodeling
MATRIX
Ground substance
Proteoglycans
Glycoproteins
Minerals
Water
Fibers

12. Cells of Bone (Primary/Temporary)
Osteoprogenitor
Osteoclast
Osteoblast
Osteocyte
Osteoid

13. PERIOSTEUM
MEMBRANE COVERING OUTER SURFACE OF BONE
LAYERS: 1. FIBROUS LAYER
2. CAMBIUM LAYER

14. OSTEOGENIC CELLS

15. OSTEOBLAST

16. OSTEOCYTE

17. OSTEOCLAST

18. Osteoclast

19. CANALICULI

20. Bone cells -Function
• Osteoblasts – Matrix synthesis – Osteoid,
Calcification
PTH receptors
• Osteocyte – Maintanace of Matrix by intercellular
sickling systems
• Osteoclast – Digestion of collagen,
dissolving hydroxyapatite
* Calcitonin receptors

21. Bone cells- Medical application
Rate of bone apposition – Bone growth
Osteomalacia – Impaired mineralization
Osteitis fibrosa cystica – osteoclast activity
Osteopetrosis – “Marble bones” – Bone resorption
defect due to osteoclastic activity
Osteitis deformans (Paget’s disease) –Uncontrolled
osteoclast activity followed by osteoblastic activity
(incomplete)- Stops at osteoid level

22. BIOCHEMISTRY
1.INORGANIC 65 -70%
2.ORGANIC 30-35%
ORGANIC: a. collagen 90-95%
b. pps 4-5%
c.Lipids 0.1%
INORGANIC 90% Calcium and phosphate

23. BONE COLLAGEN
1.AXIAL PERIODICITY OF 640 TO 700A
2.PROTIEN COMPOSITION WITH ONE THIRD GLYCINE
3.LARGE NO. OF ALANINE RESIDUES
4.CYSTEINE IS COMPLETELY ABSENT

24. Matrix
• Fibers – Collagen Type I- Gene mutation in alfa
1or 2 OSTEOGENESIS IMPERFACTA
• Ground substance
Proteoglycans – Chondroitin Sulphate,
Keratan Sulphate
Glycoproteins – Osteocalcin , Alkaline
phosphatase

25. Structural regions of long bone

26. Gross structure of typical long bone
 Shaft – Thick compact bone+ medullary cavity
 Ends- Cancellous bone + thin compact layer
 Articular cartilage – No periosteum, avascular
 Periosteum – Fibrous + cellular
Shape, nutrition, attachment
fracture repair, sensitive
 Endosteum – Cellular -Repair
and remodelling
 Nutrient foramen – mid shaft
 Bone marrow – Red, Yellow

27. Parts of a growing bone
 Epiphysis
(Secondary)
 Epiphyseal
plate
 Metaphysis
 Diaphysis
(Primary)

28. TYPES OF EPIPHYSIS

29. PRESSURE
region of the long bone that forms the joint is called Pressure Epiphysis
ARTICULAR....WT TRANSMISSON
EX: HEAD OF FEMUR AND HUMERUS
TRACTION
Non-articular
Muscle pull
Ossifies later than Pressure
.EX HUMERUS G.T AND L.T
FEMUR G.T AND LT

30. ATAVISTIC
COROCOID PROCESS OF SCAPULA
OS TRIGONUM
ABERRANT
HEAD OF 1ST METACARPEL
Unusual

31. Epiphyseal plate

32. Growth Plate

33. ZONE 1
INJURY CAUSES CESSATION OF GROWTH
ZONE 2
BONE LENGTH IS ADDED
ZONE 3
WEAKEST PORTION OF GROWTH PLATE

34. Metaphysis
 Epiphyseal end
of diaphysis
 Active growth
 Before fusion
end arteries, hair
pin bends
OSTEOMYELITI
S

35. Blood supply of bones
Long Bone
 Nutrient artery
 Metaphyseal arteries
 Epiphyseal arteries
 Periosteal arteries
Short Bone - Nutrient artery;
Periosteal arteries
Vertebra- Body, Processes
Rib - Nutrient artery; Periosteal
arteries

36. Nutrient artery
 Mid shaft
 Tortuiosity
 2/3rd inner compact bone
 Hair pin loops
 Direction – away from
growing end
.
“To the elbow I go.
From the knee I flee.”

37. Nutrient Artery
1.Enters into the diaphysis of long bones
through an oblique canal
2.direction of canal is determined by relative
amount of growth that has occurred at
proximal and distal ends of the bone;
3.does not branch within the cortex, divides
after reaching the medullary cavity,
4. direction of blood flow is centrifugal;

38. Disruption of Nutrient Artery causes
1. In growing bone can result in necrosis of large portion
of marrow & of inner two thirds of cortex
2. This cortical death does not occur in adult bone
because combined epiphyseal-metaphyseal collateral
circulation is developed enough to maintain these
areas;
3.loss of circulation in terminal vessels of nutrient artery
of growing bone will interfere with enchondral
ossification;

39. Epiphyseal arteries
In femoral and radial heads, which
are almost entirely covered by
cartilage vessels enter in region
between articular cartilage &
growth-plate cartilage
In other regions, the epiphysis has
openings that permit passage of large
number of vessels into and out of the
ossification centers

40. Obliteration of epiphyseal blood supply
causes
1.necrosis of epiphysis
2. longitudinal growth ceases
3. permanent closure of epiphyseal plate

41. METAPHYSIAL ARTERIES
BRANCHES OF SYSTEMIC VESSELS
Epiphyseal vessels are responsible for permitting longitudinal
growth to occur, whereas metaphyseal vessels nourish
osteoprogenitor cells, which lay down bone on cartilage
matrix;

42. PERIOSTEAL ARTERIES
Periosteal vessels send small branches thru minute channels in cortex to
supply about outer 1/3 of cortex
Extensive network of vessels covers entire length of the bone shaft
Anastomoses with adjacent skeletal muscles so in cases in which the
nutrient artery of muscle has been damaged, then periosteal vessels
may temporarily serve as the primary blood supply;

44. BLOOD SUPPLY OF GROWTH PLATE
growth plate itself is avascular & receives nutrition from 2 sources
1.epiphyseal vessels that supply germinal, proliferating, and upper
hypertrophic cell layers by diffusion
2 .metaphyseal vessels that supply zone of
provisional calcification

45. In a young child, epiphyseal vessels are
separated from metaphyseal vessels, but
following growth arrest of the cartilage plate,
there is
an extensive anastomoses between
epiphyseal vessels, metaphyseal vessels, &
terminal branches of Nutrient Artery;

46. VENOUS DRAINAGE
TRANSVERSE VENOUS CHANNELS
CENTRAL VENOUS SINUS
NUTRIENT VEIN
-ONLY 5-10% OF VENOUS DRINAGE IS THROUGH NUTRIENT
VEIN
-REMAINING IS THROUGH PERIOSTEAL VENOUS DRINAGE

47. Circulatory disturbances
PHYSIS AND EPIPHYSIS
1.Legg–Calve–Perthes Disease: Circulatory disturbance to the capital
femoral epiphysis
2.Physeal Trauma
METAPHYSIS
1.Haematogenous Osteomyelitis
2.Metastasis.
DIAPHYSIS
1.Intramedullary Reaming
2.Fracture Healing
PERIOSTEAL BLOOD SUPPLY
1.Paralytic conditions

48. Spongy bone
1. loose network of bone trabecule
2. interconnected
3. arranged along lines of maximum stress

49. Spongy Bone
Superimposed lamllae
No Haversian system
Lamellated trabeculae
Red marrow

50. Spongy
Bone-
No HS

51. Osteon (Haversian system)
 Central canal (Haversian
or osteonal canal)
 Transverse (Volkmann)
canals
 Lacuna
 Canaliculi ("tiny canals")
 Lamellae
Concentric,Intersititial,
Circumferential

52. Compact bone

53. COMPACT BONE

54. Sharpey’s fibers
Connective tissue matrix
Bundles of collagen fibers
Connect Perisoteum to
Bone
Fibrous layer of
Periosteum to
outer circumferential
and interstitial lamellae

55. Growing Bone
BONE GROWTH
1. Appositional
2. Endochondral

56. Factors affecting growth of a bone
 Nutritional
 Vit. A - Co-ordination of osteoblastic and
osteoclastic activity
Vit.C – Synthesis of organic matrix
Vit.D – Absorption of Ca, P
Rickets, Osteomalacia
(Calcification deficiency)
Calcium – Decalcification of bone

58. Factors affecting growth of a bone
 Hormonal –
• Pituitary - GH- Dwarfism; Gigantism,
Acromegaly
• Thyroid - Calcitonin
Parathyroid – PTH Decalcification
Sex Hormones - Androgens, estrogens - Stimulators
 Mechanical factors
Tensile forces – Bone formation
Compressive forces – Bone resorption

59. Ossification Centre

60. Rules of Ossification
 Primary centers - before birth
except carpal and tarsal (except calcaneus, talus,
cuboid)
 Secondary centers - after birth
except lower end of femur, upper end of tibia,
humerus
 Center which appears first unites last
except lower end of FIBULA

61. Rules of Ossification
 Center which appears later unites first
except upper end of fibula
 Direction of nutrient artery - away from
growing end
except fibula
 Growing end is one where center
appears first and unites last
except fibula

62. Fracture Healing 1. Hematoma
formation
Macrophages
Osteoclasts
2. Fibrocartilaginous
callus formation
Periosteum Endosteum
3. Bony callus
formation
Ossification (EC & IM)
4. Remodeling
Sec.bone formation

63. Bone remodeling cycle