Cartilage

Cartilage is a smooth and tough type of connective tissue.

It is not as hard as bone, but it is stiffer than muscle. This tissue is often covered by a tough membrane called the perichondrium. It serves many important jobs in the body. In many animals, it protects the ends of long bones at the joints. This specific kind is called articular cartilage.

It also helps keep tubes open, like the rings in your windpipe.

Cartilage works through a special mix of parts called a matrix. This matrix is made of things like collagen fibers and proteoglycans.

Tiny, specialized cells called chondrocytes live inside this matrix. These cells produce much of the material that makes up the tissue. One important part is a protein called aggrecan. Aggrecan forms large groups that hold onto water. This water helps the cartilage handle pressure and impacts. When you move, fluid flows through the tissue to help move nutrients.

Scientists study how cartilage grows and forms during early life. In the very beginning, cartilage forms from a group of cells called mesenchyme. This process is known as chondrification.

In all vertebrates, cartilage is the main skeletal tissue in early stages. Later, some parts might turn into hard bone through a process called ossification. Researchers also look at how tiny molecules called non-coding RNAs affect this growth. These molecules can play a role in health conditions like arthritis.

There are three main types of cartilage used in the body.

The first is elastic cartilage, which is found in your outer ear flaps. The second is hyaline cartilage, which is found in your nose and trachea. This type has fewer cells and more space between them. The third type is fibrocartilage, which is found in your spine and the meniscus of the knee. Fibrocartilage has the fewest cells and the most space between them. Each type has a different amount of collagen and proteoglycan.

Understanding cartilage helps us understand how our joints move every day. It acts as a bridge between soft tissues and hard bone.

This bridge prevents too much stress on your bones. However, cartilage is very difficult to fix if it gets hurt. It does not have blood vessels or nerves inside it. Because there is no blood flow, the cells cannot move to a damaged area. This means cartilage repairs itself at a very slow rate compared to other tissues.