Overview

Cartilage is a resilient and flexible form of connective tissue found throughout vertebrate bodies. It provides shape, cushioning and smooth surfaces where bones meet in joints. Unlike bone, cartilage is firm but more elastic, enabling structures such as the nose and ear to maintain form while tolerating bending.

Common locations and visible roles

In humans cartilage appears in many anatomical sites: the rib cage (costal cartilages that attach ribs to the sternum), the ear (allowing flexibility and shape), the nose, the throat (laryngeal cartilages that protect the airway), and between vertebrae where intervertebral discs contain cartilaginous tissues. Cartilage also forms growth plates in children, providing a template for later bone formation.

Structure and types

Cartilage is composed of specialized cells called chondrocytes embedded in an extracellular matrix rich in collagen fibers, proteoglycans and water. There are three principal types:

  • Hyaline cartilage: the most common type, with a glassy matrix found on joint surfaces and in growth plates.
  • Elastic cartilage: contains elastic fibers and provides greater flexibility, as in the external ear and epiglottis.
  • Fibrocartilage: dense and tough, found in intervertebral discs and certain joint cushions.

Development, nourishment and comparative examples

During embryonic development many bones form by endochondral ossification, where a cartilage model is gradually replaced by bone. Cartilage differs from most other tissues because it is avascular and typically lacks nerves; nutrients and waste products move by diffusion through the matrix. This low direct blood supply contributes to slower growth and limited self-repair. In some vertebrates, such as sharks, cartilage makes up the bulk of the skeleton; these animals belong to the class Chondrichthyes.

Functions and mechanical properties

Cartilage serves several mechanical and biological roles: it reduces friction at joint surfaces, distributes load to protect underlying bone, absorbs shock, maintains the shape of flexible structures, and forms scaffolds for bone growth in the developing skeleton. Its combination of stiffness and elasticity comes from the interaction of collagen networks and hydrated proteoglycans in the matrix.

Clinical relevance and notable facts

Cartilage is susceptible to wear, injury and degeneration. One of the most common clinical problems is osteoarthritis, in which joint cartilage thins and bones contact one another, causing pain and reduced motion. Because cartilage is relatively isolated from the immune system, with limited access by lymphocytes and circulating antibodies, small grafts can sometimes be transplanted with lower rejection risk than other tissues. Nevertheless, damaged cartilage heals poorly and is a major focus of reconstructive medicine: treatments include conservative therapies, surgical repair, grafting, and emerging tissue-engineering approaches to regenerate cartilage or replace damaged surfaces.

Further considerations

Understanding cartilage biology helps explain why joint injuries may produce long-term disability and why early intervention can be important. Research continues into biomaterials, cell therapies and surgical techniques to restore cartilage function. For general background see authoritative resources on connective tissues and clinical orthopedics, which describe both normal cartilage physiology and common pathological changes in greater detail.

connective tissue | bones | joints | rib cage | ear | nose | throat | sharks | Chondrichthyes | diffusion | osteoarthritis | lymphocytes