Articular cartilage ->
• Glassy-smooth hyaline cartilage covers the opposing bone surfaces as articular cartilage.
• These thin (1 mm or less) but spongy cushions absorb compression placed on the joint and thereby keep the bone ends from being crushed.
Joint (articular) cavity ->
• The joint cavity is a feature that is unique to synovial joints.
• It contains a small amount of synovial fluid.
• The joint cavity is a potential space because it is normally almost nonexistent, but can expand if fluid accumulates (as happens during inflammation).
Articular capsule ->
• The joint cavity is enclosed by a two-layered articular capsule, or joint capsule.
• The tough external fibrous layer is composed of dense irregular connective tissue that is continuous with the periostea of the articulating bones.
• It strengthens the joint so that the bones are not pulled apart. The inner layer of the joint capsule is a synovial membrane composed of loose connective tissue.
• Besides lining the fibrous layer internally, it covers all internal joint surfaces that are not hyaline cartilage.
• The synovial membrane's function is to make synovial fluid.
• Occupies all free space within a joint cavity and is also found within the articular cartilages, provides a slippery, weight-bearing film that reduces friction between the cartilages.
• Without this lubricant, rubbing would wear away joint surfaces and excessive friction could overheat and destroy the joint tissues.
Reinforcing ligaments ->
• Synovial joints are reinforced and strengthened by a number of bandlike ligaments.
• Most often, these are capsular ligaments, which are thickened parts of the fibrous layer.
• In other cases, they remain distinct and are found outside the capsule (as extracapsular ligaments) or deep to it (as intracapsular ligaments).
• Since intracapsular ligaments are covered with synovial membrane, they do not actually lie within the joint cavity.
Nerves and blood vessels->
• Synovial joints are richly supplied with sensory nerve fibers that innervate the capsule.
• Some of these fibers detect pain, as anyone who has suffered joint injury is aware, but most monitor joint position and stretch.
• Monitoring joint stretch is one of several ways the nervous system senses our posture and body movements (see p. 493).
• Synovial joints are also richly supplied with blood vessels, most of which supply the synovial membrane.
• There, extensive capillary beds produce the blood filtrate that is the basis of synovial fluid.
• improve the fit between articulating bone ends, making the joint more stable and minimizing wear and tear on the joint surfaces.
12th EditionElaine N. Marieb, Suzanne M. Keller 11th EditionDavid N. Shier, Jackie L. Butler, Ricki Lewis 15th EditionDavid Shier, Jackie Butler, Ricki Lewis 12th EditionDavid N. Shier, Jackie L. Butler, Ricki Lewis