The topic includes: definition and function bone classification of bone according to shape, development, region and structure gross structure of long bone parts of a bone (epiphysis, diaphysis, metaphysis and epiphysial plate of cartilage) blood supply of bone growth of a long bone

1. BONE
Vibhuti Nautiyal
MPT (Musculoskeletal)

2. Definition
• 1/3 connective tissue
• 2/3 impregnated with calcium
• Highly vascular
• Greater regenerative power
• Characteristic pattern of growth
• Mould itself according to change in stress and strain
• Constant turnover of its Ca content
• Absence of Ca salt due to acid the bone becomes flexible (tied as a ‘knot’)
• Absence of collagen due to burning the bone crumples into pieces

3. • It has two components:
Organic component Inorganic component
a) Consists of connective
tissue (collagen fibers)
a) Consists of Ca salts (Ca
phosphate, partly Ca
carbonate)
b) Tough and resilient
(flexible)
b) Hard and rigid
c) Resistant to tensile forces c) Resistant to compressive
forces of WB and impact
forces of jumping
d) salt: Calcium
hydroxyapatite

4. Function
• Gives shape and support to the body
• Resistant to any form of stress
• Provide surface for the attachment of muscles, tendons, ligaments
• Serve as levers for muscular action
• Bone marrow manufactures blood cells
• Store 97% of the body Ca and P
• Bone marrow contains reticuloendothelial cells which are phagocytic in
nature and take part in immune response of the body

5. Classification
A) According to shape:
1. Long bones:
• Has an elongated shaft (diaphysis)
• 2 expanded ends (epiphysis)
• Smooth and articular
• Has 3 surfaces, 3 borders, central medullary cavity, nutrient foramen
a) Typical long bones: humerus, ulna, radius, femur, tibia and fibula
b) Short long bones: MC, MT, Phalanges
c) Modified long bones (no medullary cavity): clavicle

7. 2) Short bones:
a) Shape is usually cuboid (cube) or scaphoid (boat)
b) Pierced by blood vessels
c) Tarsals and carpals

8. 3) Flat bones:
a) Resemble shallow plates
b) Form boundaries of certain body cavities
c) Cranium, sternum, ribs and scapula

9. 4) Irregular bones: hip bone, first and second cervical vertebra, sphenoid
5) Pneumatic bones:
a) Large air spaces lined by epithelium
b) Maxilla, sphenoid, ethmoid
c) They: i) make the skull light in weight
ii) help in resonance of voice
iii) act as air conditioning chambers
iv) improves timbre of the voice

12. 6) Sesamoid bones:
• Bony nodules
• Found embedded in the tendon or joint capsules
• No periosteum
• Ossify after birth
• Related to an articular and non- articular bony surface
• Surfaces of contact are covered with hyaline cartilage
• Lubricated by bursa or synovial membrane
• Function:
a) To resist pressure
b) To minimise friction
c) Alter the direction of pull of muscle
d) Maintain local circulation, protect the vessels and nerves
e) E.g: patella, pisiform

14. 7) Accessory bones:
• Not always present
• May occur as ununited epiphysis developed from extra centres of ossification
• Cervical rib, sutural bones of the skull
• Often bilateral
• Smooth surfaces without any callus

15. B) Developmental classification
1 a) Membrane (dermal) bones:
• Ossify in membrane
• Intramembranous or mesenchymal ossification
• Frontal, parietal and maxilla
b) Cartilaginous bones:
• Ossify in cartilage
• Intracartilaginous or endochondral ossification
• Humerus, femur, vertebraes and thoracic cage
c) Membrano- cartilaginous bones:
• Ossify partly in membrane and partly in cartilage
• Clavicle, mandible, occipital, temporal, sphenoid.

16. 2 a) Somatic bones:
• Most of the bones are somatic
b) Visceral bones:
• Develop from pharyngeal arches
• Hyoid bone, part of mandible and ear ossicles

17. C) Regional classification:
1) Axial skeleton: skull, vertebra and thoracic cage
2) Appendicular skeleton: bones of the limbs

18. D) Structural classification:
I. Macroscopically:
a) Compact:
• Dense in texture
• Extremely porous
• Best developed in the cortex of long bones
• Adaptation to bending and twisting forces
b) Cancellous:
• Open in texture
• Made up of meshwork of trabeculae (rods and plates)
• Between which are marrow containing spaces
• Types of meshwork: i) meshwork of rods
ii) Meshwork of rods and plates
iii) meshwork of plates
• Adaptation to compressive forces

20. Compact Cancellous
Location Diaphysis Epiphysis
Lamellae Arranged to form
Haversain system
Arranged in a meshwork
Bone marrow Yellow which stores fat
after puberty. Red before
puberty
Red, produce RBC’s,
granular series of WBC
and platelets

21. II Microscopically:
a) Lamellae bone (including compact and cancellous):
• Composed of thin plates of bone tissue (lamellae)
• Arranged as branching curved plates in cancellous
• Arranged as concentric cylinders in compact
b) Woven bone:
• Seen in fetal bones, fracture repair and cancer of bone
• Bone crystals and collagen fibres are arranged randomly
c) Fibrous bone:
• Found in young fetal bones
• Common in reptiles and amphibia
d) Dentine and e) cement occur in teeth

23. Gross structure
A Shaft: composed of:
• Periosteum
• Cortex
• Medullary cavity
a) Periosteum:
 thick fibrous membrane
 Covering the external surface of bone
 Made up of: i) outer fibrous layer
ii) inner cellular layer (osteogenic in nature)
 United to the underlying bone by Sharpey’s fibres
 At articular margin continuous with the capsule of joint
 Rich nerve supply
 Absent in sesamoid bone
 Function: i) osteogenic
ii) bone growth
iii) bone repair
iv) protection

25. b) Cortex:
• Made up of compact bone
• Gives it the desired strength to withstand all strain
c) Medullary cavity:
• Lined by endosteum
• Osteoblasts help in bone repair and remodelling
• Filled with red or yellow bone marrow
• Red marrow persists in the cancellous ends of long bones
• Sternum, iliac crest, vertebra, ribs
B. 2 Ends:
• Made up of cancellous bone
• Covered with hyaline cartilage

27. Parts
A Epiphysis:
• Ends and tips of a bone
• Ossify from secondary centres
I. According to number of epiphysis:
a) Simple:
• ends develop from many epiphyses
• Fuse independently with shaft
• Femur
b) Compound:
• Ends develop from many centres which unite to from a single epiphysis
• Single epiphysis fuse with the shaft
• Humerus

28. II. Based on function:
a) Pressure epiphysis:
• Articular
• Takes part in the weight transmission
• E.g: head of humerus, head of radius
b) Traction epiphysis:
• Non articular
• Does not take part in the weight transmission
• Provides attachment to one or more tendon which exert traction
• Ossify later than the pressure epiphysis
• E.g: trochanter of femur, tubercles of humerus

29. c) Ativastic epiphysis:
• An independent bone
• Fused to another bone
• E.g: coracoid process, lateral tubercle of posterior process of talus
d) Aberrant epiphysis:
• Not always present
• E.g: epiphysis at the head of Ist MC, bases of other MC bones

31. B Diaphysis:
• Elongated shaft
• Ossifies from a primary centre
• Receives blood supply from nutrient artery

32. C Metaphysis:
• Epiphyseal ends of a diaphysis
• Zone of active growth
• Richly supplied with blood through end artery forming ‘hair-pin’ ends
(before epiphyseal fusion)
• Common site of osteomyelitis (because the bacteria or emboli are easily
trapped in the ‘hair-pin’ ends)
• After epiphyseal fusion there is vascular communication between
metaphysial and epiphyseal artery, hence no more end artery because of
which no chances of osteomyelitis
• Maybe of two types:
i) Intracapsular: both ends of humerus
ii) Extracapsular: upper and lower ends of radius and ulna

34. D Epiphyseal plate of cartilage:
• Separates epiphysis from metaphysis
• Proliferation of cells in this plate is responsible for lengthwise growth of a
long bone
• After epiphyseal fusion, no longer grow in length
• Nourished by both the epiphyseal and metaphyseal artery

35. Blood supply
AArterial supply:
1) Young long bones:
a) Nutrient artery:
• Enters the shaft through the nutrient foramen
• Runs through the cortex
• Divides into ascending and descending branches
• Turn down to form hairpin bends
• Each branch divides into a number of small parallel channels
• Terminate in the adult metaphysis by anastomosing with the epiphyseal,
metaphyseal and periosteal artery
• Supplies medullary cavity, inner 2/3 of cortex and, metaphysis
• E.g: upper end of humerus, lower end of radius and ulna, lower end of femur
and upper end of tibia
• Nutrient foramen is directed away from the growing ends of bone

36. b) Periosteal artery:
• Numerous beneath the muscular and ligamentous attachments
• Ramify beneath the periosteum
• Enter the Volkmann’s canals to supply the outer 1/3 of the cortex
c) Epiphyseal artery:
• Derived from vascular arcades (circulus vasculosus)
• Found on the non articular bony surface
d) Metaphyseal artery:
• Derived from the neighbouring systemic vessels
• Pass directly into the metaphysis
• Reinforce the metaphyseal branches from the primary nutrient artery

38. 2) Long short bones:
• Nutrient artery enters the middle of shaft
• Divides to form plexus
• Infection begins in the middle of shaft
• Periosteal artery supplies major part of bone
• May replace the nutrient artery
3) Short bones:
• Supplied by numerous periosteal vessels which enter their non articular
surfaces

39. 4) Vertebra:
• Supplied by anterior and posterior vessels (body)
• Vertebral arch by large vessels entering the base of transverse process
• Red marrow is drained by 2 large basivertebral veins
5) Rib:
• Nutrient artery which enters it just beyond the tubercle
• Periosteal artery

40. B) Venous drainage:
• Numerous and large in cancellous bone
• Accompany artery in the Volkmann’s canals (compact bone)
C) Lymphatic drainage:
• Some do accompany the periosteal blood vessels
• Drain to the regional lymph nodes

41. Growth of long bone
• Length: multiplication of cells in the epiphyseal plate of cartilage
• Thickness: multiplication of cells in the deeper layers of periosteum
• Grow by deposition of new bone on the surface and at the ends (appositional
growth)
• Remodelling: unwanted bone is removed by osteoclasts