Cartilage is an elastic supporting tissue mainly of the joints but also of other body regions. Characteristic is the resistance of cartilage to mechanical impact. Anatomically remarkable is the absence of any blood supply or innervation in cartilage.
What is cartilage?
Cartilage is a connective tissue that performs support and holding functions in the body. Doctors distinguish 3 different basic types:
- Hyaline cartilage: extremely pressure-stable and elastic cartilage, especially of the joints. In addition, hyaline cartilage forms the support rings of the trachea and bronchi, as well as the basic shape of the larynx and parts of the nasal skeleton.
- Fibrocartilage: tension and pressure resistant cartilage of the disc rings and meniscus. In addition, fibrocartilage forms parts of the shoulder and jaw joint and the pubic symphysis (pelvis).
- Elastic cartilage: cartilage with a very pliable consistency. The auricle and parts of the auditory canal and epiglottis are made of elastic cartilage.
Anatomy and structure
Cartilage, for most of its volume, consists of a mass in which only a few cells are embedded. Special cartilage cells, chondrocytes, produce the basic substance of the tissue. This is why the term “cartilage matrix” is used. This matrix is formed by proteins such as the fibrous collagen as well as elastin, which has a folded sheet structure. In addition, compounds between protein and carbohydrates are involved, so-called “proteoglycans”, the most important of which is hyaluronic acid. Cartilage has neither nerves nor blood vessels running through it. The supply of oxygen and nutrients to the few cells takes place by “seepage” of tissue fluid, physically referred to as “diffusion”. From the outside, the cartilage skin, the perichondrium, carries nutrient substances. At the covering of the joints and in fibrous connective tissue, this type of supply is absent in cartilage.
Function and tasks
Cartilage is a part of the skeleton and thus serves to maintain the shape of the body. But the tissue also enables mobility and must also cushion loads. The main prerequisite for this is elasticity: even if pressure is applied and leads to temporary deformation, healthy cartilage always returns to its original shape. This becomes very clear when considering the auricles and the nose. Despite excellent elasticity, cartilage is extraordinarily stable. This can be seen in the joints, where pressure and friction lead to enormous stress. For example, ankle, knee and hip joints must absorb the shocks of walking and running without the bone splintering. The cartilage even has to withstand the bending movements of the spine: Because the connection between the vertebrae are also joints, whose cartilage is the fibrous ring of the intervertebral disc, which encases a the gelatinous disc core. The flexible cartilage fulfills several functions at the larynx. This is because the cartilaginous “larynx” supports swallowing and can close the airways with a lid. The larynx also houses the vocal cords, so the ability to speak also results from an organ made of cartilage.
Diseases and ailments
Cartilage, being a highly stressed tissue, is very susceptible to wear and tear. Admittedly, this phenomenon increases with age and is then a normal process when the thinning of the cartilage layer occurs uniformly. However, if the cartilage is subjected to one-sided stress over a long period of time, this leads to uneven wear and tear and thus to arthrosis. The cartilage-bearing bone is then always also involved. Causes are often overweight or heavy physical work. Joint malpositions also play a role. In addition to these chronic forms of progression, injuries also occur as a result of brief application of force. This often occurs in sports accidents. Also clinically relevant is the herniated disc, in which the cartilaginous fibrous ring is torn, causing the disc nucleus to leak. The resulting pressure on nerves or even the spinal cord leads to severe pain and even paralysis. Cartilage softening or chondromalacia belongs to the autoimmune diseases and thus to the rheumatic group of forms. The knee joint is predominantly affected. The joint damage often progresses to joint inflammation (arthritis). Tietze syndrome is also an inflammatory cartilage disease. In this case, fractures can even occur at the cartilaginous seams between the sternum and the ribs as a result of the inflammation.If only the cartilage is affected, this is referred to as chondrosis. These diseases are now largely placed among the “osteochondroses” because in most cases there is a joint disorder of bone and cartilage.
