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

FUNCTION 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

Hyaline Cartilage

FUNCTION Support with great tensile strength (2) White fibro-cartilage: It contains dense white fibrous tissue Chondrocytes 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

Fibrocartilage

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

FUNCTION (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

Elastic Cartilage

Traits Hyaline Fibrocartilage Elastic Appearnce Bluish white Dense white Yellow Translucensy Tarnslucent Opaque Source Modified areolar CT Mod. Collagenous CT Mod elastic CT

Traits Hyaline Fibro cartilage Elastic Composition Numerous cartilage cells & very fine collagenous fibers. Numerous coarse, wavy collagenous fibers arranged in bundles with fibroblast & some chondrocytes between Numerous elastic fibers. Few cartilage cells & collagenous fibers are also present Calcification Occurs frequently Does not occur Occurs very raely, if any