What is the term for a fluid-filled sac that helps tendons, ligaments, muscles, and skin to glide smoothly?

The term for a fluid-filled sac that aids in the smooth gliding of tendons, ligaments, muscles, and skin is known as a bursa. These structures serve a crucial role in reducing friction between moving parts in the joints. The bursa is filled with synovial fluid, which provides lubrication. This lubrication is essential during movement, allowing for easier and more fluid motion without irritation or discomfort to the surrounding tissues.

Understanding the role of the bursa is important in the context of musculoskeletal health. When a bursa becomes inflamed, a condition known as bursitis can occur, leading to pain and restricted movement. This highlights how vital these structures are for maintaining the proper function of joints and soft tissues.

The other terms—synovial membrane, cartilage, and fascia—refer to different components within the musculoskeletal system and serve unique functions, but none describe the fluid-filled sacs that specifically facilitate smooth gliding motions like a bursa does. The synovial membrane provides the fluid that fills the bursa, cartilage covers the ends of bones to prevent wear, and fascia connects muscles to each other and to the skin, but they do not fulfill the same function as the bursa in preventing friction.