synovial membrane

Examples of synovial membrane in the following topics:

• Synovial Membranes

  • A synovial membrane is the soft tissue found between the articular capsule (joint capsule) and the joint cavity of synovial joints.
  • Connective tissue membranes do not contain an epithelial cell layer and there are two forms found in the body; synovial and meninges membranes.
  • 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 morphology of synovial membranes may vary, but it often consists of two layers.
  • It is the lack of epithelial cells within the initma which defines the synovial membrane as connective rather than epithelial.

• Structure of Synovial Joints

  • The articular capsule also consists of two layers: (1) the outer fibrous membrane that may contain ligaments and (2) the inner synovial membrane that secretes the lubricating, shock-absorbing, and joint-nourishing synovial fluid.
  • Synovial fluid is the clear, viscid, lubricating fluid secreted by synovial membranes.
  • The morphology of synovial membranes may vary, but it often consists of two layers.
  • Where the underlying subintima is loose, the intima sits on a pliable membrane called the synovial membrane.
  • The synovial bursa is a small, fluid-filled sac lined by synovial membrane containing synovial fluid.

• Nerve and Blood Supply

  • Synovial joints are highly innervated but vascularized indirectly by nearby tissues.
  • Numerous vessels from this plexus pierce the fibrous capsule and form a rich vascular plexus in the deeper part of the synovial membrane.
  • The blood vessels of the synovial membrane terminate around the articular margins in a fringe of looped anastomoses termed the circulus vasculosus (circulus articularis vasculosus).
  • It supplies the capsule, synovial membrane, and the epiphyses.
  • The synovial cartilage in the capsule acts somewhat like a sponge.

• Bursae and Tendon Sheaths

  • 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.

• 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.

• Fibrous Joints

  • Synovial joints are those in which the bones are not directly joined.
  • These joints have a synovial cavity and are united by the dense irregular connective tissue that forms the articular capsule normally associated with accessory ligaments.
  • It also pumps blood and lymph from the periodontal membrane into the dental veins and lymph channels and stimulates sensory nerve terminals in the membrane to send signals to the brain centers that control the muscles of mastication.
  • Differentiate among the three classifications of joints: fibrous, cartilaginous, and synovial

• 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.

• Syndesmoses

  • For example, the long bones of the lower arm and the leg both have attached interosseous membranes.
  • The muscles in the leg are separated into sections in the front and back with this membrane.
  • The strength of the membrane allows absorption and distribution of impacts to either bone.
  • The interosseous membrane in the lower arm extends between the radius and the ulna.
  • Located directly above the ankle joint, which is a synovial hinge joint, the ankle syndesmosis is held together by four ligaments.

• Rheumatism and Arthritis

  • Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks flexible (synovial) joints .
  • The process involves an inflammatory response of the capsule around the joints (synovium) secondary to swelling (hyperplasia) of synovial cells, excess synovial fluid, and the development of fibrous tissue (pannus) in the synovium.
  • Rheumatoid arthritis can also produce diffuse inflammation in the lungs, the membrane around the heart (pericardium), the membranes of the lung (pleura), and the white of the eye (sclera), and also nodular lesions, most common in subcutaneous tissue.

• 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.