Cartilage is the main scaffold component of early embryos. With the development of the fetus, it is gradually replaced by bones, and this replacement process continues until a period of time after birth. It is a specialized dense connective tissue, and the intercellular substance is hard and elastic. In adults, only some cartilage is scattered, and its function varies with location. Cartilage is a viscous gelatinous substance, strong but more elastic than bone. It is the main component of the bones of many protozoa such as sharks. In humans, the nose and ears contain cartilage for filling tissues. Translucent and elastic tissue that forms the bones of vertebrate embryos and very small larvae. Most higher vertebrates are transformed into bones, but primitive species (such as sturgeon and gill fish) remain for life and are the main components of bones.

First, hyaline cartilage (hyaline cartilage)

The matrix of hyaline cartilage contains only a small amount of collagen fibers, which is rich in matrix and translucent when fresh. Mainly distributed in articular cartilage, costal cartilage and so on.

Fibrocartilage: Fibrocartilage is distributed in intervertebral disc, articular disc and pubic symphysis. The matrix is rich in collagen fiber bundles, which are arranged in parallel or staggered. Chondrocytes are small and few, arranged in rows between collagen fiber bundles. In the HE staining section, the fibers were dyed red, so it was not easy to see the cartilage matrix, only the deeply stained cartilage sac and a small amount of lightly stained basophilic matrix could be seen around the chondrocytes.

Third, Elastic cartilage (elastic cartilage)

Elastic cartilage is distributed in auricle and epiglottis. The structure is similar to hyaline cartilage, and only contains a large number of elastic fibers interwoven into a net in the matrix. The fibers in the middle of cartilage are dense and rare in the periphery. This kind of cartilage has good elasticity.

Fourthly, periochondrium.

In addition to the surface of articular cartilage, cartilage is covered with a dense layer of connective tissue, that is, perichondrium. Its outer fiber is dense, which mainly plays a protective role; The inner layer is loose and rich in cells, nerves and some small blood vessels. Another kind of immature cells (stem cells) can form bone or cartilage in the perichondrium near cartilage, which is spindle-shaped and can proliferate and differentiate into chondrocytes. The perichondrium can protect and nourish cartilage, and it also plays an important role in cartilage growth.