Synonyms in a broader sense
- Cartilage Cell
- Chondrocyte
- Arthrosis
Definition
Cartilage is a special form of connective tissue. A distinction is made between different forms of cartilage, which is adapted to the respective function. The most important function of cartilage is as a joint surface in the joint and the intervertebral disc.
Introduction
Cartilage is mainly found in the skeleton and respiratory tract. Due to its structure and its physical and chemical properties, it occupies an intermediate position between connective and bone tissue. It has a high compressive strength, is viscoelastically deformable and has a high resistance to shear forces.
Characteristic for cartilage tissue are the cartilage cells (chondroblasts and chondrocytes). These are more or less rounded and lie in small groups (chondrons) directly in the cartilage (in a so-called extracellular matrix) so that they do not have any contact with each other. The cartilage cells are equipped with the usual cell organelles.
Remarkable here are the many glycogen particles for anaerobic energy production (i.e. energy production without oxygen) and occasionally individual large fat droplets. This is important because the cartilage is usually not supplied with blood and therefore has only little oxygen available. The most important components of the actual cartilage substance in which the cartilage cells are located – the extracellular matrix – are proteoglycans and collagen fibrils.
Both substances are special substances that only occur in this form in cartilage. The compressive elasticity of cartilage tissue comes from the interaction of the proteoglycans and collagen fibers. In adults, the cartilage is free of blood vessels. The supply of the necessary nutrients takes place exclusively by diffusion either through a vascular cartilage skin (perichondrium) or directly through the synovial fluid (synovia).
Cartilage growth
The formation of a cartilaginous structure begins when connective tissue cells (mesenchymal cells) are closely packed together and differentiate into cartilage cells (chondroblasts). They then produce cartilage matrix and thus become chondrocytes. As the cartilage matrix increases, the cells are forced apart and form collagen fibrils.
This process is called interstitial growth. This leads to rapid enlargement of the cartilaginous structure and takes place mainly in the early phase of cartilage formation and in the growth plate. After interstitial growth is complete, the chondrocytes resulting from the last cell divisions remain together in groups.
They are separated from each other only by thin matrix skins. Chondrocytes of the cartilage tissue no longer divide. On the outside of the cartilaginous system, mesenchymal cells form connective tissue cells (fibroblasts) and form a connective tissue capsule (perichondrium).
Undifferentiated cells remain on the inner layer of this capsule from which chondroblasts can develop and which ensure growth by attaching new cartilage. The attachment from the outside is called appositional growth. superficial cartilage layer middle cartilage layer
- Superficial cartilage layer
- Middle cartilage layer
- Calcifying cartilage layer
- Bones