Tendon

A tendon or sinew is a strong, fibrous tissue that connects muscle to bone. It plays a vital role in helping our bodies move by transferring the forces generated by muscle contractions to the bones. This allows us to bend, stretch, and perform many everyday actions smoothly.

Tendons are made primarily of a protein called collagen, which gives them their strength and flexibility. They are different from ligaments, which connect bone to bone. The human body contains around 4,000 tendons, working together to support our musculoskeletal system.

These remarkable tissues can withstand a lot of tension, or pulling force, without breaking. Understanding tendons helps us appreciate how our bodies function and why it's important to take care of our muscles and bones through proper exercise and nutrition.

Structure

A tendon is a strong tissue that connects muscle to bone. It is made of special cells called tendon cells, which create a substance called collagen. Collagen fibers in tendons line up in the same direction and are grouped together. These groups are held together by thin layers of tissue, and the whole tendon is covered by a layer of fascia.

Tendons are mostly made of collagen, which gives them strength. They also contain other materials that help them stay flexible and connect the collagen fibers. These include substances like elastin and proteoglycans. The collagen fibers in tendons come together to form larger structures, and proteoglycans help hold these fibers together. Tendon cells produce collagen and communicate with each other to help the tendon respond to stretching and movement.

List of tendons

The human body contains around 4,000 tendons. These tough tissues connect muscles to bones, helping us move. A table lists 55 of these important tendons, showing just a small part of what our bodies use to stay strong and active.

Functions

Tendons are strong tissues that connect muscles to bones, helping us move. They let muscles pull on bones to make our bodies move, and they can also store energy to make movement more efficient. For example, when we walk, the Achilles tendon in our heel stretches and then releases energy to help us take each step.

Tendons are made mostly of a material called collagen, which gives them strength and flexibility. They can stretch a little and then go back to their original shape, acting like tiny springs. This helps our muscles work with less effort and gives us better control over our movements.

Clinical significance

Tendons can get hurt in many ways, often from doing too much activity. These injuries are called tendinopathies and can make tendons weak or even break them. There are different kinds of tendinopathies, like tendinosis, which is when the tendon gets damaged inside without swelling, and tendinitis, which is when the tendon gets inflamed and swollen.

When a tendon gets injured, it can still heal. The healing process has three main steps. First, the body sends special cells to clean up the injury. Then, the cells start to build new tissue to fix the tendon. Finally, the new tissue gets stronger and more like normal tendon tissue. Even though it takes time, tendons can recover and get stronger again with the right care and activity.

Society and culture

Sinew, a strong material from tendons, was very useful in old times before factories. People used it for sewing, attaching feathers to arrows, and making tools. It was especially important for Inuit and other cold-weather people who didn’t have other fibers. Some hunters used sinew in special bows for better accuracy.

Tendon is also eaten in some Asian foods. For example, beef tendon is a part of dishes like suan bao niu jin and can be found in Vietnamese phở.

Other animals

In some animals, like birds and certain dinosaurs, parts of the tendon can turn into bone. This happens when special cells called osteocytes move into the tendon and start building bone, similar to how bone forms in places like the kneecap. In birds, this mainly happens in the legs, while in some dinosaurs, it helped support their tails.