• žBones & cartilage
  • žMade up of specialised connective tissue c/a skeletal tissue
  • žCan bear weight and has considerable tensile strength
  • žConsists of same components ( general connective tissue) but here the matrix is solidified
  • žFunctions- rigid framework, protection to viscera, leverage for movement

Types of skeleton

  • žAxial– close to central axis: skull, ear ossicles, hyoid, vertebral column, rib cage
  • žAppendicular- pectoral girdle, pelvic girdle, upper limb & lower limb bones


  • žHighly vascular mineralised conn. Tissue
  • žConsists of cells and dense intercellular organic matrix impregnated with inorganic salts
  • žOrganic material- collagen fibres. Provides tensile strength.
  • žInorganic – calcium phosphate, traces of other salts. Provides hardness & rigidity
  • žLiving part, regenerate, diseased, atrophy & hypertrophy
  • žRigid framework of body to give shape & support
  • žAttachment to muscles, tendons, ligaments
  • žAct as levers
  • žProtection to viscera
  • žContain marrow which forms blood cells
  • žStorehouse of calcium & phosphorus
  • žHelp in resonance of voice

Microscopic Structure

 Cells- 4 cell types

  • žOsteoprogenitor cells
  • žOsteoblasts
  • žOsteocytes
  • žOsteoclasts

Fibers -type I collagen fibers

Ground substance-

Water, Protein(calcium binding),  Chondroitin Sulfate,  Crystalized Mineral Salts (Calcium Phosphate)

Classification of Bone

  • žAccording to shape
  • žAccording to structure
  • žAccording to development

a. shape

  • žLong bones- typical: humerus, radius, etc.    miniature:  metacarpals & metatarsals
  • žShort bones: carpal & tarsal
  • žFlat bones: b of thoracic cage, cranial vault
  • žIrregular bones: hip bone, vertebrae
  • žPneumatic bones: maxilla, frontal, sphenoid, ethmoid
  • žSesamoid bones: patella, fabella, pisiform
  • žAccessory bones: wormian , os trigonum, os vesalinum
  • žHeterotopic bone: rider’s bone

Sesamoid bones

Bony nodules developed in certain muscle tendons when they are rubbed against bony surface during movement of joint.

Sites: patella at knee jt., fabella behind the knee jt., pisiform in flexor carpi ulnaris, one in tendon of peroneus longus at cuboid, head of I metcarpal in tendon of adductor longus, etc.

Functions: act as a pulley for muscle contraction, alter the direction of pull of muscle, minimize the frictionof tendon against bone

Characteristics: develop in tendon of muscle, no periosteum, ossify after birth, lack haversian system

B. Structural

  • žMacroscopically- compact, cancellous
  • žMicroscopically- woven, lamellar

Compact/ dense

  • žDense ivory like
  • žConsists of haversian system/osteon and lamella of collagenous sheet

Lacunae, Canaliculi, Volkmann’s canals present

Cancellous bone

  • Meshwork of bony spicules
  • Consists of interconnecting rods & plates of bone called trabeculae enclosing large spaces filled with red bone marrow
  • Don’t have osteon
  • Wolff’s law
  • Pressure lamellae
  • Tension lamellae
  • Bony buttresses

c. developmental

  • žMembranous
  • žCartilaginous
  • žMembrano cartilaginous

Gross structure of a typical long bone

  • 3 parts- a shaft & two ends
  • Shaft – elongated part, made up of outer compact bone enclosing medullary cavity filled with yellow bone marrow
  • Ends – made up of cancellous bone covered by a thin shell of compact bone, takes part in joint formation

  • Periosteum & endosteum- contain osteoprogenitor cells, osteoblast & osteoclast
  • Sharpey’s fibres
  • Nutrient foramen
  • Bone marrow- soft , loose, vascular tissue consisting of delicate network of reticular fibers and various type of cells
  • Red & yellow
  • Gelatinous marrow

Parts of a growing young (long) bone

  • Epiphysis
  • Epiphyseal plates
  • Metaphyses
  • Diaphysis

Types of epiphyses

  • žPressure- head of femur, humerus, lower end of radius
  • žTraction-greater & lesser trochanters of humerus
  • žAtavistic- coracoid process, posterior tubercle of talus
  • žAberrant- epiphysis at end of I metacarpal

Blood supply

  • Long bone– nutrient, periosteal, metaphyseal, epiphyseal


  • Simple/ closed
  • Compound
  • Repair

Development & growth

  • žProcess of bone formation
  • žFrom mesenchyme
  • žIntramembranous
  • žIntracartilaginous

Ossification of a long bone

  • Growing end of long bone
  • Law of ossification
  • Growth of a long bone-appositional, endo chondral
  • Remodelling
  • Factors affecting growth- nutritional, hormonal, genetic, mechanical

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