Bursae are defined as which of the following?

• A. Flattened sacs that serve as a protective buffer between bones and overlapping muscles (deep bursae) or between bones and tendons/skin (superficial bursae)
• B. Tendon sheaths wrapping around tendons
• C. Dense fibrous capsules around joints
• D. Sacs that store excess synovial fluid

Answer: (A)

Bursae are small, flattened sacs lined with synovial membrane and filled with a small amount of lubricating fluid. Their job is to cushion and reduce friction between moving structures, acting as protective buffers. They sit in places where there’s potential friction between bones and muscles, or between bones and tendons or skin. That’s why you have deep bursae between a bone and a neighboring muscle or tendon, and superficial bursae between a bone and overlying skin or soft tissue.

This matches the described definition because it emphasizes their role as friction-reducing cushions between bones and soft tissues. Other structures—the tendon sheaths that wrap around tendons, the dense fibrous capsules around joints, or sacs that merely “store” fluid—are distinct anatomical features with different functions, so they don’t define bursae.