cartilage & bone, mbbs 1st year
DESCRIPTION
for 1st year mbbs studentsTRANSCRIPT
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