The four principal types of bones are long, short, flat and irregular. Bones that are longer than they are wide are called long bones. They consist of a long shaft with two bulky ends or extremities.

1. Bones
&
Classification
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2. Objectives
• Skeleton
• Bone
• Microscopic structure
• Characteristics
• Classifications of bone
• Gross structure
• Epiphyses
• Blood supply
• MCQ
• Clinical Vignettes
• References
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3. Skeleton
Form a rigid frame work of body
Composed of :-
Bones
Cartilages
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Made up of specialised supporting
connective tissue called Sclerous
(skeletal) tissue

4. Types of Skeleton
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5. Axial skeleton
• Skull
• Ear ossicles
• Hyoid bone
• Sternum
• Vertebral
column
• Rib cage
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6. Appendicular
skeleton
• Bilaterally symmetrical
Comprises bone
• Upper limb and
• Lower limb
with bony girdles
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7. Bone
• Os (Latin)
• Osteon ( Greek)
Hard structure , form rigid framework of body
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8. Structurally
Highly vascular mineral connective tissue
• Specialized form of connective tissue
Distinguish feature from other connective tissues is
Mineralization of its matrix
Mineral is calcium phosphate hydroxyapatite crystals
[Ca10(PO4)6(OH)2].
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10. Microscopic Structure
• Cells
• Ground substance + fibre , form the extracellular
substance or matrix
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11. Bone Matrix
Organic (no calcified )
• Type 1 collagen
• Non mineralized ground
substance
1. Chondroitin sulfate
2. Keratin sulfate
• Provide resilience
Inorganic (calcified)
• Contain crystalline
mineral salt (calcium ,
phosphorus)
• Osteoid undergo
mineralization process
• Provide hardness and
rigidity
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12. Ground substance or Matrix
1. Mainly type I collagen and types III,XI,XIII collagens in
trace amount
Other matrix, (Noncollagenous)proteins that constitute
ground substance of bone.
• Proteoglycan macromolecules
• Multiadhesive glycoprotein's
• Bone-specific, vitamin K–dependent proteins
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Both collagen and ground substance become mineralized to form
bone tissue

13. Cells
Osteoproginator
cells
• Osteoblast
• Osteocytes
• Osteoclast
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Bone matrix contains lacunae connected by a
network of canaliculi

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16. Characteristics
• Living tissue
• Highly vascular
• Serves as a storage site for calcium and
phosphate
• Supply by nerve and blood vessel
• Show pattern of growth
• Subjected to disease & heal after fracture
• Regenerative power
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17. Classification of bone
• According to shape
• According to structure
• According to development
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18. • Acc to shape of bone
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19. 1. Long bone
• Typical long bones
humerus, radius, ulna, femur, tibia, fibula;
• Miniature long bones have only one epiphysis
e.g. metacarpals, metatarsals and phalanges;
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20. 2. Short bones:
Shape is usually cuboid, cuneiform,
Trapezoid or scaphoid.
Examples: tarsal and carpal bones
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21. 3. Flat bones
Shallow plates
Form boundaries of body cavities.
Examples:
Vault of skull, ribs,
sternum & scapula
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22. 4. Sesamoid bone
Bony nodules found embedded in tendons or joint
capsules.
No periosteum and ossify after birth
Functions are:
(a) To resist pressure & friction
(c) To alter direction of pull of muscle
(d) To maintain local circulation.
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23. 5. Irregular bone
• Vertebrae
• Sacrum , coccyx
• Temporal , sphenoid, ethmoid, zygomatic,
maxilla, mandible, palatine, inferior nasal
concha,
• Hyoid
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24. 6. Pneumatic bone
Irregular bones contain large air spaces lined by epithelium
examples: maxilla, sphenoid, ethmoid.
Function:-
Make skull light in weight,
Help in resonance of voice,
Act as air conditioning chambers for inspired air
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25. 7. Accessory bone (supernumerary bone)
Not always present .
Developed from extra-centres of ossification.
Examples: Sutural bones, os trigonum
(lateral tubercle of talus),os vesalianum
(tuberosity of 5th metatarsal)
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26. Structural classification
Macroscopically,
• Compact bone
• Cancellous bone
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27. Compact bone consist of
• Lamella of collagenous sheet
• Haversian system or osteon
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28. Cancellous bone/ spongy bone
• Meshwork of bony spicules.
• Do not form haversian system
• Architecture of cancellous bone is depend upon
trajectory theory (Wolf’s law)
Pressure lamellae Tension lamellae
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31. Microscopically
Classification is based on arrangement of different
component in matrix are arranged
• Woven bone – Collagen fasiscle and bony crystal
arranged in mesh network, like woven fabric e.g, callus
bone , young fetal bone
• Lamellar bone- Mineralized matrix arranged in layer of
thin sheet e.g. All adult bone
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32. Woven bone lamellar bone
• Lamellar appearance - arrangement of collagen fibres
• Woven bone is weak- repair of fracture

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34. Gross structure
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35. Epiphyses
• Type of epiphyses
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36. Blood Supply
Supplied by following 4 set of
Arteries
• Nutrient arteries
• Metaphyseal arteries
• Epiphyseal
• Periosteal arteries
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37. Developmental classification
• Membranous bones
• Cartilaginous bones
• Membrano- Cartilaginous bones
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Types of bones Examples
Membranous Bones of cranial vault
Facial bones
Cartilaginous Bone of limbs
Bones of base of skull
Bones of vertebral column
Bones of thoracic cage
Membrano-cartilagnous Mandible
Clavicle

38. Intramembranous Ossification
Develop from mesenchymal model
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40. Intra-cartilaginous Ossification
• Develop from cartilaginous ossification
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41. Intra-cartilaginous Ossification
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42. Clinical
• Paget’s disease
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43. MCQ
Mainly all bone in the body is made up of both
compact and spongy bone, except
a) Clavicle
b) Inferior nasal choncha
c) Patella
d) fabella
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a) Inferior nasal choncha

44. Name muscle in which fabella bone usually develop?
a) Lateral head of Gastrocnemius
b) Long head of biceps femoris
c) Popliteus
d) Adductor longus
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a) Lateral head of Gastrocnemius

45. Clinical Vignettes
A 7 year old boy come to an orthopaedics clinic, having a fever,
swelling and redness over knee, complain of fatigue and having a
history trauma few weeks ago. An X-ray reveal a lesion over tibia,
Doctor diagnose a osteomyelitic lesion.
Q Name the part of growing long bone commonly effected by
osteomyelitis?
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Ans Metaphysis

46. A 12 year old child born with a condition called
Cleidocranial dysostosis, as shown in image.
Q what type of development is shown by clavicle?
a) Cartilaginous development
b) Membranous development
c) Membrano – cartilaginous
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Membranous development

47. References
• Vishram Singh general anatomy e.2014
• Histology_ A Text and Atlas_ With Correlated
Cell and Molecular Biology, 6th Edition
• Keith L. Moore Clinically Oriented Anatomy,
Sixth Edition .
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