The structural and functional unit of a skeletal muscle is a:

Choice A reason: Tendons connect muscles to bones and transmit force during contraction. They do not act as cushions or reduce friction.

Choice B reason: Bursae are the correct answer. These are small fluid-filled sacs lined with synovial membrane that reduce friction between moving structures such as tendons and bones or skin and bones. They are commonly found near joints like the shoulder, elbow, and knee.

Choice C reason: Menisci are fibrocartilaginous pads found in certain joints like the knee. They help distribute weight and improve joint stability but are not fluid-filled sacs.

Choice D reason: Joint cavities are spaces within synovial joints that contain synovial fluid. While they allow movement, they are not separate cushioning structures like bursae.

Choice E reason: Ligaments connect bones to other bones and stabilize joints. They do not serve as cushions or reduce friction.

Choice A reason: Tendons attach muscles to bones, not to articular cartilage. Cartilage does not serve as an attachment site for tendons.

Choice B reason: Red blood cells are produced in the red bone marrow, which is found in spongy bone, not in articular cartilage.

Choice C reason: Articular cartilage is composed of hyaline cartilage and covers the ends of bones in synovial joints. It provides a smooth, lubricated surface for articulation and acts as a cushion to absorb compressive forces during movement.

Choice D reason: Bone length increases through growth at the epiphyseal plate, not through articular cartilage.

Choice E reason: The synovial membrane lines the joint capsule and produces synovial fluid. It is a separate structure from articular cartilage.