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Cartilage. Dr. PARDEEP KUMAR. CARTILAGE It is a specialized form of connective tissue consists of cells, fibres & ground substance. The cells are embedded in the intercellular matrix Origin - Mesenchymal in origin. Cartilage. Embryo More prevalent than in adult
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Cartilage Dr.PARDEEP KUMAR
CARTILAGE • It is a specialized form of connective tissue consists of cells, fibres & ground substance. The cells are embedded in the intercellular matrix • Origin - Mesenchymal in origin.
Cartilage • Embryo • More prevalent than in adult • Skeleton initially mostly cartilage • Bone replaces cartilage in fetal and childhood periods
Location of cartilage in adults • External ear • Nose • “Articular” – covering the ends of most bones and movable joints • “Costal” – connecting ribs to sternum • Larynx - voice box
Epiglottis – flap keeping food out of lungs • Cartilaginous rings holding open the air tubes of the respiratory system (trachea and bronchi) • Intervertebral discs • Pubic symphysis • Articular discs such as meniscus in knee joint
Composition: • 1) Cells: Chondrocytes, Chondroblasts • 2) Fibres: White fibers and yellow elastic fibres. • 3) Ground substance: Consists of Glyco-samino-glycans: • i) Chondroitin sulfate. • ii) Kerato sulfate. • iii) Hyaluronic acid.
Characteristics of cartilage • Avascular, devoid of lymphatics & nerves. Gets its nutrition from blood vessels of adjacent tissue by process of diffusion • Its matrix is not calcified ( Cartilage turn into bone by calcification) • Cartilage grows by 2 methods • Interstitial (endogenous method) • Appositional (exogenous growth) • It forms skeleton of body in early life, most of which is replaced by bone in adult
Growth of a cartilage Cartilage grows by 2 methods • Interstitial growth: Expansion of internal mass of cartilage by division of chondrocyte ("in the middle“) Increasing in LENGTH; chondrocytes divide and secrete matrix from w/in lacunae • Appositional growth: when cartilage grows by adding new layer on its surface by the cells of perichondium ("at the edge“) • Increasing in WIDTH; chondroblasts deposit matrix on surface of pre-existing cartilage
Functions of Cartilage • Supports soft tissues of body • Facilitates bone movement by virtue of its smooth surface Nutrition of Cartilage • Cartilage is avascular • Hyaline & elastic cartilage gets nutrition from vessels of Perichondrium • Fibro cartilage gets nutrition from blood vessels of surrounding connective tissue & articular cartilage from synovial fluid
Perichondrium ( covering of cartilage) • Dense fibrous connective tissue which encloses cartilage is called Perichondrium • It is essential for the growth & maintenance of cartilage
CHONDROCYTES & CHONDROBLASTS • They are cartilage cells, irregular in shape. • The almond shaped spaces they occupy are lacunae. • They may remain in ground substance widely separated as discrete or in groups. • They are developed from mesenchymal cells.
Types of cartilage: 3 • Hyaline cartilage: flexible and resilient • Chondrocytes appear spherical • Lacuna – cavity in matrix holding chondrocyte • Collagen the only fiber • Elastic cartilage: highly bendable • Matrix with elastic as well as collagen fibers • Epiglottis, larynx and outer ear • Fibrocartilage: resists compression and tension • Rows of thick collagen fibers alternating with rows of chondrocytes (in matrix) • Knee menisci and annunulus fibrosis of intervertebral discs
Types: Three types of CARTILAGE (1) Hyaline cartilage: • It is translucent so called hyaline • Fibres are scanty, relatively cellular i,e more Chondrocytes with more ground substance. • FUNCTION • Support tissue and organs
Examples of Hyaline Cartilage: • Articular cartilage • Costal cartilage • Trachea, bronchi, • Nasal cartilage etc
(2) White fibro-cartilage: • It contains dense white fibrous tissueChondrocytes in more collagen fibre, few ground substance. • FUNCTION • Support with great tensile strength
(2) White fibro-cartilage: Examples: • Inter vertebral disc, • Glenoid & Acetabular Labrum • Pubic symphysis etc
Intervertebral Discs • It is a fibrocartilaginous disc, situated between the bodies of 2 vertebrae & held to them by means of ligament.
It has 2 component Annulus fibrous / outer cartilaginous • It has external layer of dense connective tissue, but is mainly composed of overlapping lamina of cartilage Nucleus pulposus/ Inner liquid • It is situated in the centre of annulus fibrosus. It consists of few rounded cells embedded in amorphous fluid rich in hyaluronic acid
Functions • They allow certain amount of movement between vertebrae • They act as shock absorber • They prevent friction between corresponding vertebrae • They contribute about 1/5th of total length of the vertebral column
(3) Yellow elastic cartilage: • It is a modified elastic connective tissue in which elastic fibers are numerous • More yellow elastic fibres, Chondrocytes in scanty ground substance. Examples: • External ear, • Epiglottis, • Auditory tube, • Some laryngeal cartilage • FUNCTION • Support with flexibility