Tendons and Bursas

Tendons are tough bands of connective tissue made up mostly of a tough protein called collagen. They do not stretch. Tendons firmly attach each end of a muscle to a bone. They are located within sheaths, which are lubricated to allow the tendons to move without disturbing surrounding tissue.

Bursas are small fluid-filled sacs that lie under a tendon, cushioning the tendon and protecting it from injury. Bursas also provide extra cushioning to adjacent structures that otherwise might rub against each other, causing wear and tear--for example, between a bone and a ligament.