What do you understand by cartilage ? In how many groups are they divided?



The cartilage is a solid but semi-rigid and flexible skeletal (connective) tissue, containing a clear matrix of a firm material, the chondrin. The cartilage is bounded externally by a stiff sheath, the perichondrium, consisting of white fibrous tissue. The cartilages are of three types :
(i) Hyaline cartilage: It contains a clear, homogenous, translucent, bluish green matrix. This cartilage is flexible. It forms articular surfaces at the joints of long bones, where it is called articular cartilage. It also form part of larynx, sternum, rings of trachea, nasal cartilages etc.
(ii) Fibrous cartilage : It has well developed fibres in the matrix. It is of two types: white fibrous cartilage and elastic cartilage.
White fibrous cartilage has little matrix and abundant parallel white fibres. It occurs in the intervertebral discs, where it act as cushions. Elastic cartilage has abundant yellow fibres with white fibres. It is more flexible than any other cartilage. It is found in ear pinna, external auditory canal of ear, eustachian tubes, epiglottis etc.
(ili) Calcified cartilage : It has calcium salts deposited in the matrix. The calcium salts make it hard and inelastic. It is found in suprascapula of pectoral girdle of frog and vertebrae of shark.