Final answer:
The functions of synovial fluid include lubrication, shock absorption, and nourishment of articular cartilage within the joint.
Step-by-step explanation:
Friction between the bones at a synovial joint is prevented by the presence of articular cartilage, a thin layer of hyaline cartilage that covers the entire articulating surface of each bone. The cells of the synovial membrane secrete synovial fluid, a thick fluid that provides lubrication to reduce friction between the bones of the joint. This fluid also nourishes the articular cartilage. Additionally, synovial fluid provides shock absorption within the joint, protecting the bones from damage.