synovial fluid

Examples of synovial fluid in the following topics:

• Structure of Synovial Joints

  • Synovial fluid is the clear, viscid, lubricating fluid secreted by synovial membranes.
  • The main structural differences between synovial and fibrous joints are the existence of capsules surrounding the articulating surfaces of a synovial joint and the presence of lubricating synovial fluid within those capsules (synovial cavities).
  • The water component of synovial fluid is effectively trapped in the joint space by the hyaluronan due to its large, highly negatively charged moieties.
  • The macrophages are responsible for the removal of undesirable substances from the synovial fluid.
  • The synovial bursa is a small, fluid-filled sac lined by synovial membrane containing synovial fluid.

• Bursitis

  • Bursitis, the inflammation of bursae (small sacs) of synovial fluid, impedes the movement of muscles and tendons over joint bones.
  • Bursitis is the inflammation of one or more bursae (small sacs) of synovial fluid in the body .

• Bursae and Tendon Sheaths

  • Joints are cushioned by small fluid-filled sacs called bursae and stabilized by tough bands of fibrous connective tissue called tendons.
  • Synovial joints are made up of five classes of tissues: bone, cartilage, synovium, synovial fluid, and tensile tissues composed of tendons and ligaments.
  • The synovial lining in the bursae and tendon sheaths, similar to that within joints, is a slippery, non-adherent surface allowing movement between planes of tissue.
  • Synovial tendon sheaths line tendons only where they pass through narrow passages or retinacula, as in the palm, at the wrist, and around the ankle.
  • A bursa (plural bursae) is a small, fluid-filled sac lined by synovial membrane with an inner capillary layer of fluid (synovial fluid) with the consistency of raw egg white.

• Synovial Membranes

  • A synovial membrane is the soft tissue found between the articular capsule (joint capsule) and the joint cavity of synovial joints.
  • The synovial membrane (or synovium) is the connective tissue which lines the inner surface of the capsule of a synovial joint and secretes synovial fluid which serves a lubricating function, allowing joint surfaces to smoothly move across each other.
  • The type B synoviocytes manufacture a long-chain sugar polymer called hyaluronan, which makes the synovial fluid together with a molecule called lubricin, which lubricates the joint surfaces.
  • The water component of synovial fluid is effectively trapped in the joint space by the hyaluronan, due to its large, highly negatively charged moeties.
  • The type A synoviocytes are responsible for the removal of undesirable substances from the synovial fluid.

• Structural Classification of Joints

  • They have a lesser range of movement than synovial joints.
  • These joints (also called diarthroses) have a synovial cavity.
  • Synovial cavities are filled with synovial fluid.
  • The knees and elbows are examples of synovial joints.
  • This diagram of a synovial joint delineates the articular cartilage, articular capsule, bone, synovial membrane, and joint cavity containing synovial fluid.

• Synovial Joint Movements

  • Synovial joints allow an individual to achieve a wide range of movements.
  • Synovial joints achieve movement at the point of contact of the articulating bones.
  • The main structural differences between synovial and fibrous joints are the existence of capsules surrounding the articulating surfaces of a synovial joint and the presence of lubricating synovial fluid within those capsules (synovial cavities).
  • Several movements may be performed by synovial joints.
  • There are six types of synovial joints.

• Classification of Joints on the Basis of Structure and Function

  • This space, referred to as the synovial (or joint) cavity, is filled with synovial fluid.
  • Synovial fluid lubricates the joint, reducing friction between the bones and allowing for greater movement.
  • Knees, elbows, and shoulders are examples of synovial joints.
  • Since they allow for free movement, synovial joints are classified as diarthroses.
  • Synovial joints are the only joints that have a space or "synovial cavity" in the joint.

• Nerve and Blood Supply

  • Synovial joints are highly innervated but vascularized indirectly by nearby tissues.
  • It supplies the capsule, synovial membrane, and the epiphyses.
  • The synovial cartilage in the capsule acts somewhat like a sponge.
  • A sponge will absorb fluid, but it will release little of that fluid unless it is squeezed.
  • Flexing and extending the joint alternately squeezes the sponge and releases it to reabsorb more fluid.

• Stability and Range of Motion at Synovial Joints

  • Disuse, causing decrease in synovial fluid, flexibility of ligaments and tendons, and muscle atrophy
  • Aging is another factor that influences motion due to decreased fluid, thinning of cartilage, shortening of ligaments, and loss of flexibility.

• Functional Classification of Joints

  • Diarthrosis – These are the freely-movable synovial joints.
  • Synovial joints are further classified based on the different types of movement they provide, including:
  • Image of a skeleton and skematics of the different classes of synovial joints.