Biology: Cartilage Structure and Composition

Cartilage Structure and Composition

• 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.

Perichondrium

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

Cartilage Types

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

Hyaline 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.

Fibrocartilage

• 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)

Elastic Cartilage

• 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 and Calcification

• 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.