What are bursae?

• A. Nerve endings around the joint
• B. Bones forming joints
• C. Flattened sacs that cushion joints, lined with synovial membranes
• D. Muscle fibers holding joint together

Answer: (C)

Bursae are small, flattened sacs that cushion joints and reduce friction during movement. They are lined with a synovial membrane and filled with synovial fluid, providing a slippery surface so tendons, muscles, and skin can glide smoothly over bone. This cushioning helps prevent wear and irritation as joints move. They are not nerve endings, bones, or muscle fibers, which is why the description of flattened sacs lined with synovial membranes best fits what bursae are.