This document discusses different tissues associated with bones, joints, and muscles. It describes fascia as a connective tissue beneath the skin that attaches, stabilizes, and separates muscles. It also describes bursae as fluid-filled sacs that function as gliding surfaces to reduce friction between moving tissues and protect structures as they cross bony areas. Finally, it defines a motor unit as a motor nerve and the muscle fibers it supplies, describing how nerve impulses travel from the spinal cord along the motor nerve and trigger muscle contraction through calcium release within muscle fibers.