Cartilage is a type of dense connective tissue. It is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix composed of collagen fibers, abundant ground substance rich in proteoglycan, and elastin fibers. Cartilage is classified in three types, elastic cartilage, hyaline cartilage and fibrocartilage, which differ in the relative amounts of these three main components.
Cartilage is found in many areas in the body including the articular surface of the bones, the rib cage, the ear, the nose, the bronchial tubes and the intervertebral discs. Its mechanical properties are intermediate between bone and dense connective tissue like tendon.Unlike other connective tissues, cartilage does not contain blood vessels. The chondrocytes are fed by diffusion, helped by the pumping action generated by compression of the articular cartilage or flexion of the elastic cartilage. Thus, compared to other connective tissues, cartilage grows and repairs more slowly.
A tough, elastic, fibrous connective tissue found in various parts of the body.Â A major constituent of the embryonic and young vertebrate skeleton, it is converted largely to bone with maturation.
Types Of Cartilage:
- Hyaline cartilage
Hyaline cartilage is found on the surfaces of movable joints, and its primary function is to minimize friction between moving bones. The cells of hyaline cartilage are called chondrocytes, and these cells are busy building new materials to keep the cartilage healthy
- Elastic cartilage
1 – cells of the cartilage (chondrocytes, chondroblasts)
2 – intercellular cartilage matrix
Elastic cartilage contains large amounts of elastic fibers (elastin) scattered throughout the matrix. It is stiff yet elastic, and is important to prevent tubular structures from collapsing. Elastic cartilage is found in the pinna of the ear, in tubular structures such as the auditory (Eustachian) tubes and in the epiglottis.
Fibrocartilage is characterized by a dense network of Type I collagen. It is a white, very tough material that provides high tensile strength and support. It contains more collagen and less proteoglycan than hyaline cartilage. Thus, its properties are closer to those of tendons than hyaline cartilage. It is present in areas most subject to frequent stress like intervertebral discs, the symphysis pubis and the attachments of certain tendons and ligaments.
Diseases and treatment:
There are several diseases which can affect the cartilage. They are given below:
Osteoarthritis , Achondroplasia , Costochondritis , Spinal disc herniation , & Relapsing polychondritis.
Cartilage has limited repair capabilities, because chondrocytes are bound in lacunae, they cannot migrate to damaged areas. Therefore if damaged, it is difficult to heal. Also, because hyaline cartilage does not have a blood supply, the deposition of new matrix is slow. Damaged hyaline cartilage is usually replaced by fibrocartilage scar tissue. Over the last years, surgeons and scientist have elaborated a series of cartilage repair procedures that help to postpone the need for joint replacement..