Synovial joint

Examples of Synovial joint in the following topics:

• Synovial Joint Movements

  • Synovial joints allow an individual to achieve a wide range of movements.
  • A synovial joint, also known as a diarthrosis, is the most common and most movable type of joint in the body of a mammal.
  • 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.

• 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:
  • An example is the elbow joint.
  • An example is the hip joint.
  • Image of a skeleton and skematics of the different classes of synovial joints.

• Structural Classification of Joints

  • They have a lesser range of movement than synovial joints.
  • They allow more movement than fibrous joints but less than that of synovial joints.
  • These joints (also called diarthroses) have a synovial cavity.
  • 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.

• Structure of Synovial Joints

  • A synovial joint or diarthrosis occurs at articulating bones to allow movement.
  • A synovial joint, also known as a diarthrosis, is the most common and most movable type of joint in a mammal's body.
  • A synovial membrane (or synovium) is the soft tissue found between the articular capsule (joint capsule) and the joint cavity of synovial joints.
  • As with most other joints, 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).

• Nerve and Blood Supply

  • Synovial joints are highly innervated but vascularized indirectly by nearby tissues.
  • The blood supply of a synovial joint comes from the arteries sharing in anastomosis around the joint.
  • It supplies the capsule, synovial membrane, and the epiphyses.
  • The synovial cartilage in the capsule acts somewhat like a sponge.
  • Exercising the joint, in effect, squeezes the synovial "sponge", allowing gas exchange to occur and nutrients to flow into the cartilage.

• Types of Synovial Joints

  • There are six different types of synovial joint based on their shapes, each allowing a different kind of movement.
  • There are six basic types of synovial joints.
  • Some synovial joints are relatively immobile but stable.
  • The types of the synovial joints are based on their shapes and can be classified as plane, hinge, pivot, condyloid, saddle, and ball-and-socket.
  • The atlanto-axial joint, proximal radioulnar joint, and distal radioulnar joint are examples of pivot joints.

• 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 morphology of synovial membranes may vary, but it often consists of two layers.
  • 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.

• 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.
  • 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.
  • It provides a cushion between bones and tendons or muscles around a joint.
  • Bursae are found around most major joints of the body, such as the shoulder and the knee.

• Fibrous Joints

  • Fibrous joints are also called fixed or immovable joints because they do not move.
  • 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.
  • These joints are also called fixed or immovable joints because they do not move.
  • Differentiate among the three classifications of joints: fibrous, cartilaginous, and synovial

• Cartilaginous Joints: Synchodroses

  • Cartilaginous joints allow more movement between bones than a fibrous joint but less than the highly mobile synovial joint.
  • The joint between the manubrium and the sternum is an example of a cartilaginous joint.
  • Where the connecting medium is hyaline cartilage, a cartilaginous joint is termed a synchondrosis or primary cartilaginous joint.
  • A synchondrosis joint is the first sternocostal joint (where the first rib meets the sternum).
  • The rest of the sternocostal joints are synovial plane joints.