Typical Synovial Joint

A "typical" synovial joint is one which has parts common to all of the synovial joints. In a sense, it is imaginary. It is not actually a specific synovial joint. It is a composite. It is illustrated in figure 4-2. The "typical" synovial joint has the following parts:

a. Bones. Bones are the levers of motion. They are the site of attachment for skeletal muscles.

b. Articular Cartilages. The "contact" points of the bones are usually covered with a layer of lubricated cartilage. Where these cartilages end, the synovial membranes begin. Cartilages provide a smooth surface to reduce friction.

Figure 4-2. A "typical synovial joint:--diagrammatic. c. Synovial Membrane, Space, and Fluid.

(1) Synovial membrane. The synovial membrane lines the inner surface of the capsule. It secretes synovial fluid into the synovial space.

(2) Synovial space. Figure 4-2 exaggerates the amount of space between the bones. The space within the capsule allows movement.

(3) Synovial fluid. Synovial fluid is a colorless, viscous fluid similar in consistency to raw egg white. It lubricates the articulation.

d. Capsule. The "typical" synovial articulation is surrounded by a sleeve of dense FCT known as the capsule. The capsule encloses the articulation.

e. Ligaments. Primarily, ligaments hold bones together. Ligaments also may help restrain motion in certain directions and stabilize the articulation.

f. Muscles. Skeletal muscles apply the forces to produce a given motion.

NOTE: See table 4-1 for a summary of the structures in a "typical" synovial articulation, the tissues composing each structure, and the actions attributed to each structure.

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