What structure protects the body by forming a small fluid-filled sac at pressure points?

The bursa is a small fluid-filled sac that plays a crucial role in reducing friction and cushioning pressure points in the body, particularly between bones and tendons or muscles. It serves as a protective structure that allows for smooth movement and minimizes wear and tear on tissues when joints are in motion. This is particularly important in areas of the body that experience high levels of stress and movement, such as the shoulders, elbows, and knees.

The bursa is filled with synovial fluid, which provides lubrication and further aids in absorbing shocks and pressures that occur during physical activity. This protective function is vital in maintaining joint health and mobility.

In contrast, tendons connect muscles to bones, ligaments connect bones to other bones, and cartilage provides cushioning and support at joints but does not form fluid-filled sacs. Each of these structures plays its own unique role in the musculoskeletal system, but only the bursa is responsible for forming fluid-filled sacs specifically to protect areas under pressure during movement. This distinction highlights the importance of the bursa in maintaining functional integrity and preventing injury in various parts of the body.