Anatomy & Physiology

Anatomy & Physiology Study Guide

©2018 Achieve Page 98 Synovial joints have a variety of accessory structures, including pads of cartilage or fat, ligaments, tendons, and bursae. Cartilages and fat pads lie between the opposing articular surfaces. The synovial joint has a pad of fibrous cartilage between its opposing bones called a meniscus . Fat pads are superficial to the joint capsule and localized masses of adipose tissue covered by a layer of synovial membrane. Fat pads function as packing material for the joint and fill in the spaces created when the bones move and the joint cavity changes shape. Ligaments support, strengthen, and reinforce synovial joints. Ligaments are very strong. In a sprain, some of the collagen fibers of a ligament are torn, but the ligament survives and the joint is not damaged. With excessive force, one of the attached bones usually breaks before the ligament tears. In general, a broken bone heals better and faster than a torn ligament because ligaments have no direct blood supply and thus must obtain essential substances by diffusion. Tendons passing across or around a joint may limit the joint’s range of motion and provide mechanical support for it. For example, tendons associated with the muscles of the arm provide much of the bracing for the shoulder joint. of 368 Articular Cartilages The bony surfaces at a synovial joint do not contact one another because the articulating surfaces are covered by special articular cartilages. Articular cartilages resemble hyaline cartilages with their slick and smooth surfaces. This protective feature reduces friction during joint movement. Synovial Fluid Synovial fluid resembles interstitial fluid, but contains a high concentration of proteoglycans secreted by fibroblasts of the synovial membrane. The synovial fluid within a joint has three functions: it reduces friction between moving surfaces, it continuously provides nutrients and a waste-disposal route for the chondrocytes of the articular cartilages, and it absorbs shock in joints that are subjected to compression. Ac esso y Structures