cartilage & bone, mbbs 1st year

Histology of

Cartilage

CARTILAGE

CARTILAGE

CARTILAGE

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.

Hyaline CartilageFeatures: 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.

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.

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.

BONE - I

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

Classification of Bones

According to shape:

1. Long bones: Two ends called epiphysis & an intervening

part diaphysis.

Contain nutrient foramen directed away from the growing end.

a) Typical long bone: Humerus, radius, ulna, femur, tibia, & fibula;

b) Miniature long bone: metacarpals, metatarsals & phalanges; &

c) Modified long bones: clavicle.

2. Short bones:

Shape is cuboid, cuneiform, trapezoid, or scaphoid.

Carpal & tarsal bones.

3. Flat bones: vault of the skull, ribs, sternum & scapula.

4. Irregular bones: vertebrae, hip bone & bones in the base of the skull.

5. Pneumatic bones: Maxilla,

sphenoid, ethmoid, etc.

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

Developmental classification

1. Membrane bone: Ossify in membrane, derived from mesenchymal

condensations. E.g. bone of vault of skull & facial bones.

2. Cartilaginous bone: Ossify in cartilage & derived from the preformed

cartilaginous models. E.g. bones of limbs, vertebral column & thoracic cage.

3. Membrano-cartilaginous bones: Partly in membrane & partly in cartilage. E.g. clavicle, mandible, occipital, temporal, sphenoid.

Regional classification:

1. Axial skeleton: skull, vertebral column & ribs

2. Appendicular skeleton: bones of the limbs.

Structural classification:

1. Macroscopically

1. Compact bone,

2. Cancellous bones

2. Microscopically

1. Lamellar bone,

2. Fibrous bone,

3. Dentine &

4. Cement.

Gross structure of an adult long bone

1. Shaft:

1. Periosteum

2. Cortex

3. Endosteum

4. Medullary cavity

2. Two ends

Parts of a young bone:

Epiphysis: ends of bone, ossify from sec. centre of ossification.

1) Pressure epiphysis: head of femur, lower end of radius, etc.

2) Traction epiphysis: trochanters of femur & tubercles of humerus.

3) Atavistic epiphysis: coracoid process of scapula.

4) Aberrant epiphysis: epiphysis at the head of the first metacarpal & at the bases of other metacarpal bones

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.

Blood supply of bones

For long bone:

• Epiphysial artery

• Metaphysial artery

• Periosteal artery

• Nutrient artery

Histologyof

compact bone

Cells of Bone

1. Osteoprogenitor cells: stem cells of mesenchymal origin that can proliferate & convert themselves into osteoblasts.

2. Osteoblasts: bone forming cells derived from osteoprogenitor cells & responsible for laying down the organic matrix of bone.

3. Osteocytes: cells of mature bone.

4. Osteoclasts: bone removing cells found in relation to surfaces where bone removing is taking place.

Cells of Bone

Histology of compact bone