The structure of joint Article Abstract
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Published: March 02, 2008
The understanding of arthritis and what it can mean will be made easier if you know the basic structure of the joints. First of all, a joint is where two bones meet. Alohough there are several types of joints, these may be divided into two categories: firstly, those which don''t move very much and are without a cavity; secondly, those which move freely and do have a joint cavity.
The first type is called a synarthrosis and consists of fibrous tissue, cartilage (a kind of gristle) or a combination of the two. Examples of these may be found in the gead and spinal column, Since the second typ of joint is mostfrequently affected by arthritis, it is important to understand what it is and how it works in a little more detail. This is the commonest type of joint in the body - a synovial joint or diarthrosis- and can be found in the shoulder, elbow, wrist, finger, hip, knee, ankle and toe.
some of these are formed by more than two but the principles of their strructure are the same. Where the bone ends touch is covered by gristle or cartilage. This articular cartilage has a smooth, polished surface which eliminates a lot of friction. It is somewhat elastic and, because it has no nerves and thus can''t ''feel'', this means that the everyday stresses of joint movements can be carried out without pain. The touching of this pair of surfaces is essential for the joint to work, one surface being concex(curved outward), the other concave (curved inward). Loss of this perfect ''mating'' leads to the cartilage deteriorating with only feeble attempts by the body to repair it .
To help maintain the joint in good working order, a tough fibrous capsule forms the walls of the joint , which are then firmly attached to the touching bones. Ligamensts, tendons and muscles provide further support to the joint, guiding and resstraining mpvements. The capsule has a strong resistance to disease but w3eak powers of healing. Lining thje inhside of the capsule is a thin, glistening layker that covers all the surfaces within the joint , except the cartilage. This is the synovial m embrane that produces a small amout of clear, straw-coloured, sticky fluid. The two most important functions of this synovial fluid are the ''oiling'' of the joint surfaces when they move and feeding the structures within the joint, particularly the articular cartilage. In contrast to the capsule, the synovial membrane has a rich blood supply and good powers of rep;air. The cartilage itself lacks both blood vessels and nervers. Nerves are contained in both the synovial membane kand capsule, in the former transkittingt pain, and in ther latter giving the brain additional information about both the position of resting joint and .the degree of motion in a moving one. You can test this awareness of what vour joints are doing, even with your eyes closed.
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