articular cartilage

(noun)

A tough, elastic, fibrous connective tissue found in various parts of the body such as the joints, outer ear, and larynx. A major constituent of the embryonic and young vertebrate skeleton, converted largely to bone with maturation.

Related Terms

Examples of articular cartilage in the following topics:

  • Development of Joints

    • Articular cartilage is a flexible material found between bones at movable joints.
    • Articular cartilage function is dependent on the molecular composition of its extracellular matrix (ECM), which consists mainly of proteoglycans and collagens.
    • Articular cartilage is maintained by embedded chondrocytes that comprise only 1% of the cartilage volume, and remodeling of cartilage is predominantly affected by changes and rearrangements of the collagen matrix, which responds to tensile and compressive forces experienced by the cartilage.
    • At the joint, the epiphysis is covered with articular cartilage; below that covering is a zone similar to the epiphyseal plate, known as subchondral bone.
    • Histological image of the hyaline cartilage which coats the articular surfaces of joints.

  • Bone and Joint Disorders

    • Arthritis may arise from aging, damage to the articular cartilage, autoimmune diseases, bacterial or viral infections, or unknown (probably genetic) causes.
    • The most common type of arthritis is osteoarthritis, which is associated with aging and “wear and tear” of the articular cartilage.
    • Osteoarthritis begins in the cartilage and eventually causes the two opposing bones to erode into each other.
    • As the disease progresses, the articular cartilage is severely damaged or destroyed, resulting in joint deformation, loss of movement, and severe disability.

  • Classification of Joints on the Basis of Structure and Function

    • Cartilaginous joints are those in which the bones are connected by cartilage.
    • In a synchondrosis, the bones are joined by hyaline cartilage.
    • The ends of the bones are covered with articular cartilage, a hyaline cartilage.
    • The entire joint is surrounded by an articular capsule composed of connective tissue.
    • Articular capsules may also possess ligaments that hold the bones together.

  • Structure of Synovial Joints

    • In these joints, the contiguous bony surfaces are covered with articular cartilage and connected by ligaments lined by synovial membrane.
    • This articular cartilage functions to absorb shock and reduce friction during movement.
    • A synovial membrane (or synovium) is the soft tissue found between the articular capsule (joint capsule) and the joint cavity of synovial joints.
    • In any one position, much of the cartilage is close enough to get nutrition directly from the synovium.
    • Some areas of cartilage have to obtain nutrients indirectly and may do so either from diffusion through cartilage or by the stirring of synovial fluid.

  • Structural Classification of Joints

    • A joint, also known as an articulation or articular surface, is a connection that occurs between bones in the skeletal system.
    • Cartilaginous joints are connected by fibrocartilage or hyaline cartilage.
    • Their bones are connected by dense irregular connective tissue that forms an articular capsule surrounding the bones’ articulating surfaces.
    • This diagram of a synovial joint delineates the articular cartilage, articular capsule, bone, synovial membrane, and joint cavity containing synovial fluid.
    • Image demonstrates a synchondrosis joint with epiphyseal plate (temporary hyaline cartilage joint) indicated (a) and a symphysis joint (b).

  • Structure, Type, and Location of Cartilage

    • The division of cells within cartilage occurs very slowly, and thus growth in cartilage is usually not based on an increase in size or mass of the cartilage itself.
    • Articular cartilage function is dependent on the molecular composition of its ECM, which consists mainly of proteoglycans and collagens.
    • Hyaline cartilage is the most widespread cartilage type and, in adults, it forms the articular surfaces of long bones, the rib tips, the rings of the trachea, and parts of the skull.
    • Hyaline cartilage is covered externally by a fibrous membrane, called the perichondrium, except at the articular ends of bones; it also occurs under the skin (for instance, ears and nose).
    • Elastic cartilage has the most ECM; hyaline a middle amount; and fibrous cartilage has the least amount of ECM.

  • Patellofemoral Stress Syndrome

    • The result is thinning and softening of the articular cartilage under the patella and/or on the medial or lateral femoral condyles, synovial irritation and inflammation, and subchondral bony changes in the distal femur or patella known as "bone bruises".

  • Supply of Blood and Nerves to Bone

    • These in turn drain to various channels through all surfaces of the bone except that covered by articular cartilage.
    • Epiphyseal and metaphyseal arteries enter on both sides of the growth cartilage, with anastamoses between them being few or absent.
    • Growth cartilage receives its blood supply from both sources and also from an anastamotic collar in the adjoining perichondrium.
    • Image shows the location of the epiphyseal plates (or lines) and the articular surfaces of long bones.

  • Nerve and Blood Supply

    • The articular and epiphyseal branches of the neighboring arteries form a periarticular arterial plexus.
    • The articular capsule is highly innervated but avascular (lacking blood and lymph vessels), and receives nutrition from the surrounding blood supply via either the slow process of diffusion or convection, a far more efficient process.
    • The blood vessels of the synovial membrane terminate around the articular margins in a fringe of looped anastomoses termed the circulus vasculosus (circulus articularis vasculosus).
    • The synovial cartilage in the capsule acts somewhat like a sponge.
    • Exercising the joint, in effect, squeezes the synovial "sponge", allowing gas exchange to occur and nutrients to flow into the cartilage.

  • Parts of a Vertebra

    • Comprised of bone and cartilage, the configuration of a vertebra varies based on its location within the body, although there are common features associated with those of the upper region.
    • Four articular processes originate from the joint between the pedicles and laminae, two point superiorly and two point inferiorly. 
    • They interact with the zyhapophysis, a socket for the articular processes, of the adjacent vertebrae to make the spine more stable and to facilitate a small degree of articulation.