Cartilage is a type of connective tissue composed of special cells known as chondrocytes along with collagen or yellow elastic fibers. The fibers and the cells are embedded in a firm gel like matrix rich in mucopolysaccharides. Cartilage is not as hard and rigid as bone. It is much more flexible and elastic.
Characteristic features of cartilage:
- Cartilage has no blood vessels or lymphatics and the nutrition of the cells diffuses through the matrix. This explains the slowness of healing process in cartilages.
- Cartilage has no nerves and therefore it is insensitive.
- Cartilage is surrounded by a fibrous membrane known as the perichondrium. This perichondrium is similar to the periosteum in structure and function. The articular cartilage has no perichondrium and thus its regeneration after injury is inadequate because the perichondrium plays a major role in regeneration of the cartilage.
- When a cartilage calcifies the chondrocytes die and the cartilage is replaced by bone like tissue.
- Calcium salts are not present in cartilage matrix. Instead it has flexible material known as chondroitin which provides flexibility to it.
Types of cartilage:
There are three types of cartilage;
- Hyaline cartilage
- Fibrous cartilage
- Elastic cartilage
Link to image source: Cartilage
This type of cartilage has very thin fibers having same refractive index as the matrix of the cartilage and thus these fibers are not seen. Hyaline cartilage is the articular cartilage of long bones, sternum, ribs etc. Its color is bluish white and it is flexible.
This type of cartilage has numerous white fibers. It is present in the symphysis pubis, and sternoclavicular joint etc. Its color is glistening white and the appearance is opaque.
This type of cartilage has numerous yellow elastic fibers. It is present in the ear pinna, external auditory meatus, Eustachian tubes, and epiglottis etc. Its color is yellowish and the appearance is opaque.