There are mobile (synovial), half-mobile (cartilaginous) and fixed (fibrous) bone joints. Synovial (flexible) joint provides mobility of the bones in

Bone joints (synovial, cartilaginous, fibrous) [Types]

There are mobile (synovial), half-mobile (cartilaginous) and fixed (fibrous) bone joints.

Synovial (flexible) joint provides mobility of the bones in different directions. Man has nearly 230 synovial joints. Each of them has (diagram 17): the articular surfaces of bones, cartilage, bag (capsule) and the cavity. Articular surface of bones is covered with cartilage. In healthy humans, it is elastic, smooth; it reduces friction between the bones during movement. Forms of both articular surfaces correspond to each other (diagram 19): if the surface is convex (articular head) on a bone, then on the other, it is concave, respectively (glenoid cavity). Emergent appropriateness of the structure and coordinated functionality of the human body joints provide the most favorable conditions for the movement. For example, the shoulder joint, which serves wide movements in many planes and directions, has a spherical shape (diagram 18). The knee joint, whose high mobility is dangerous (you can fall when walking), resembles a uniaxial hinge.

Synovial joint capsule — strong elastic connective tissue. Its value is dual: it keeps the bones strong and prevents dislocation of the compound, and the cells of its inner surface produces a fluid that lubricates the joint surfaces and reduces friction between the cartilage of the articular surfaces of bones. During the inflammation of the joint, production of this liquid is reduced or even stopped and the joint seems dried. It causes pain, limits movement in it.

Diagram 17. The synovial joint structure plan: 1 — articular surfaces of bones; 2 — articular cartilage; 3 — joint capsule; 4 — the joint cavity containing liquid
Diagram 18. A variety of movements of the shoulder joint

Cartilaginous (half-mobile) joint is formed by the cartilage between the vertebral bodies. Elastic cartilage protects the spine from injury, excessive stretching and compression.

Fibrous (fixed) joint of bones — is one in which there is a layer between the bones of the connective tissue, or gristle. The slit or cavity between them is absent. They have a great elasticity, but limited mobility. An example of bones fixed joint are the seams between the skull bones.

Bones joint is also provided by ligaments (diagram 20) — thick bundles that are formed by elastic connective tissue. They are cross-mounted from one bone to the other, thereby strengthening the joints and limiting their excessive mobility and prevents sprains. Taken from

Diagram 19. Various forms of joint: 1 — cylinder; 2 — block; 3 — spherical; 4 — ellipse
Diagram 21. Hand skeleton with interarticular cords (1)
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