Tendon

A tendon is a strong band of dense regular connective tissue that links a skeletal muscle to a bone, or now and then to another structure such as the eyeball. Its collagen fibers run in tight parallel bundles, which makes a tendon extremely hard to pull apart along its length.

At the muscle end, the connective tissue sheaths that wrap muscle fibers and their bundles merge with the collagen of the tendon. At the other end, the tendon fuses with the periosteum covering the bone. When the muscle contracts, the force travels through the tendon and tugs on the bone, producing movement at a joint. Some muscles attach instead through a broad, flat sheet called an aponeurosis. Where tendons cross a joint, fluid-filled tendon sheaths let them glide with little friction.

Tendons have a limited blood supply, so they heal slowly. Inflammation of a tendon, called tendinitis, often follows overuse and is common at the shoulder, elbow, wrist, knee and heel, where the Achilles tendon anchors the calf muscles. Students often mix up tendons and ligaments: tendons join muscle to bone, while ligaments join bone to bone.