Cartilage and bone are composed of different types of cells and matrices. Cartilage includes hyaline, elastic, and fibrocartilage which are distinguished by their matrix composition and distributions in different parts of the body. Bone provides structure, protection and acts as a calcium reservoir. Bones are classified based on their shape, development, and location in the body. The histology of long bones includes a periosteum, cortex, endosteum, marrow cavity, and epiphyses at each end. Bone cells include osteoprogenitors, osteoblasts, osteocytes, and osteoclasts which play different roles in bone formation and resorption.

1. Histology of Cartilage

2. CARTILAGE

3. CARTILAGE

4. CARTILAGE

5. Cartilage General features: Cells of cartilage – chondrocytes. No blood vessels or lymphatics. No nerves. Surrounded by a fibrous membrane called perichondrium. When cartilage calcifies, chondrocytes die & the cartilage is replaced by bone.

6. Hyaline Cartilage Features: Intercellular substance is homogenous. Contains numerous collagen fibers. Cells are usually present in groups (of two or more), called cell nests or isogenous cell groups. Distribution: Costal cartilages, Articular cartilage, Thyroid, cricoid & arytenoid cartilages, Nasal septum & lateral wall of nose, Epiphyseal plate of cartilage.

7. Elastic Cartilage Matrix contains elastic fibers that form a network. Distributions: Auricle or pinna, Lateral part of EAM, Medial part of auditory tube, Epiglottis, Corniculate & Cuneiform.

8. Fibrocartilage Numerous collagen bundles. No perichondrium over the cartilage. Distributions: Intervertebral discs, Pubic symphysis, Manubriosternal joint, Articular discs – TMJ, sternoclavicular joint, Glenoidal labrum & acetabular labrum.

9. BONE - I

10. Functions of bone Give shape & support to the body & resist all forms of stress. Provide surface for the attachment of muscles, tendons, ligaments, etc. Serve as levers for muscular actions. Protect visceral organs. Bone marrow manufactures blood cells. Store 97% of the body calcium & phosphorus. Bone marrow contains R-E cells. Paranasal air sinuses affect the timber of the voice

11. Classification of Bones According to shape: Long bones: Two ends called epiphysis & an intervening part diaphysis. Contain nutrient foramen directed away from the growing end. Typical long bone: Humerus, radius, ulna, femur, tibia, & fibula; Miniature long bone: metacarpals, metatarsals & phalanges; & Modified long bones: clavicle.

13. 2. Short bones: Shape is cuboid, cuneiform, trapezoid, or scaphoid. Carpal & tarsal bones.

14. 3. Flat bones: vault of the skull, ribs, sternum & scapula. 4. Irregular bones: vertebrae, hip bone & bones in the base of the skull.

15. 5. Pneumatic bones: Maxilla, sphenoid, ethmoid, etc.

16. 6. Sesamoid bones: patella, pissiform, fabella, etc. Functions: To resist pressure; To minimize friction; & To alter the direction of pull of the muscle. 7. Accessory bones: Sutural bones

17. Developmental classification Membrane bone: Ossify in membrane, derived from mesenchymal condensations. E.g. bone of vault of skull & facial bones. Cartilaginous bone: Ossify in cartilage & derived from the preformed cartilaginous models. E.g. bones of limbs, vertebral column & thoracic cage. Membrano-cartilaginous bones: Partly in membrane & partly in cartilage. E.g. clavicle, mandible, occipital, temporal, sphenoid.

18. Regional classification: Axial skeleton: skull, vertebral column & ribs Appendicular skeleton: bones of the limbs. Structural classification: Macroscopically Compact bone, Cancellous bones Microscopically Lamellar bone, Fibrous bone, Dentine & Cement.

20. Gross structure of an adult long bone Shaft: Periosteum Cortex Endosteum Medullary cavity Two ends

21. Parts of a young bone: Epiphysis: ends of bone, ossify from sec. centre of ossification. Pressure epiphysis: head of femur, lower end of radius, etc. Traction epiphysis: trochanters of femur & tubercles of humerus. Atavistic epiphysis: coracoid process of scapula. Aberrant epiphysis: epiphysis at the head of the first metacarpal & at the bases of other metacarpal bones

22. Parts of a young bone….. Diaphysis: shaft of a long bone, ossify by primary centre of ossification. Metaphysis : epiphysial end of diaphysis, zone of active growth. Epiphysial plate of cartilage: separate epiphysis from diaphysis. it causes increased length of bone.

23. Blood supply of bones For long bone: Epiphysial artery Metaphysial artery Periosteal artery Nutrient artery

24. Histology of compact bone

25. Cells of Bone Osteoprogenitor cells: stem cells of mesenchymal origin that can proliferate & convert themselves into osteoblasts. Osteoblasts: bone forming cells derived from osteoprogenitor cells & responsible for laying down the organic matrix of bone. Osteocytes: cells of mature bone. Osteoclasts: bone removing cells found in relation to surfaces where bone removing is taking place.

26. Cells of Bone

27. Histology of compact bone