Cartilage Structure and Composition

Study Notes

Cartilage is a tough but flexible tissue that makes up the main type of connective tissue in the body.
It is composed of 65-80% water, which decreases with age, and a gel-like substance called the matrix.
The matrix gives cartilage its form and function, providing firmness and resilience.

The perichondrium is a dense layer of fibrous connective tissue that covers many types of cartilage in the body.

Cartilage is made up of a dense extracellular matrix (ECM) with a sparse distribution of highly specialized cells called chondrocytes.
The ECM is primarily composed of water, collagen, and proteoglycans, with other non-collagenous proteins and glycoproteins present in lesser amounts.

There are three types of cartilage: hyaline, fibrocartilage, and elastic cartilage.

Hyaline cartilage has a high proportion of amorphous matrix.
It is the most widespread type and plays an important part in the growth in length of long bones.
It is slippery and smooth, helping bones move smoothly past each other in joints.
It is flexible but strong enough to help joints hold their shape.
Locations: articular surfaces of movable joints, walls of respiratory tracts, costal cartilages, and epiphyseal plates of long bones.

Fibrocartilage has many collagen fibers embedded in a small amount of matrix.
It is found in the discs within joints (e.g. temporomandibular joint and knee joint) and on the articular surfaces of the clavicle and mandible.
Its main function is to act as a cushion within joints, managing compression forces and reducing stress on joints.
Locations: secondary cartilaginous joints (e.g. pubic symphysis, annulus fibrosis of intervertebral discs), medial and lateral menisci of the knee joint, and locations where tendons and ligaments attach to bone.

Elastic cartilage possesses large numbers of elastic fibers embedded in matrix.
It is flexible and found in the auricle of the ear, external auditory meatus, auditory tube, and epiglottis, and tip of the nose.