Biology: 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 in older people, and a gel-like substance called the matrix.
The matrix gives cartilage its form and function, being responsible for its firmness and resilience.

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

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

Has a high proportion of amorphous matrix.
The most widespread type, resembling glass.
Plays an important part in the growth in length of long bones.
Found in articular surfaces of movable joints, respiratory tracts, costal cartilages, and epiphyseal plates of long bones.
Has a slippery and smooth surface, helping bones move smoothly past each other in joints.
Flexible but strong enough to help joints hold their shape.

Has many collagen fibers embedded in a small amount of matrix.
Found in discs within joints (e.g., temporomandibular joint and knee joint) and on the articular surfaces of the clavicle and mandible.
Acts as a cushion within joints, helping manage compression forces and reducing stress on joints.
Locations include:
- Secondary cartilaginous joints (e.g., pubic symphysis, annulus fibrosis of intervertebral discs)
- Medial and lateral menisci of the knee joint
- Location where tendons and ligaments attach to bone
- Ulnar Triangular Fibrocartilage complex (TFCC)

Possesses large numbers of elastic fibers embedded in matrix.
Found in the auricle of the ear, external auditory meatus, auditory tube, and epiglottis, and tip of the nose.
Flexible due to the presence of elastic fibers.

Cartilage cells, or chondrocytes, are contained in cavities in the matrix called cartilage lacuna.
Hyaline cartilage and fibrocartilage tend to calcify or even ossify in later life.