Definition

A joint, or articulation, is the location where two or more bones meet. 4-8. TYPES OF JOINTS

Joints are classified according to the kind of material holding the bones together and the relative freedom and kind of motion at the particular joint.

a. Fibrous Joints. Varying degrees of motion, from none to some, are possible in fibrous joints.

(1) Syndesmosis. When the bones are held together by FCT (fibrous connective tissue), the joint is referred to as a syndesmosis.

SYN = together

DESMOS = fiber (a tying material) Example: The inferior tibio-fibular joint.

(2) Suture. When the bones are quite close together with a minimum of FCT, the joint is known as a suture. Example: the joints between the cranial bones.

b. Bony Joints. Should the bones be united by bony material, the joint is referred to as a synosteosis.

SYN = together

OSTEO = bone

Example: The frontal bone. (The frontal bone of the skull is actually a bony fusion of two bones. Approximately 10 percent of the time, this fusion fails to take place; the original suture between the bones remains and is called a metopic suture.)

c. Cartilagenous Joints. These are also nonmovable joints.

(1) Synchondrosis. A cartilagenous joint in which the bones are held together by hyaline cartilage.

SYN = together CHONDRO = cartilage

Example: Epiphyseal plate.

(2) Symphysis. A cartilagenous joint in which the bones are held together by a disc of fibrocartilage.

Example: Pubic symphysis.

d. Synovial Joints. In the synovial type of joints, the bones move on one another so as to allow various motions of the body parts. The "ovial" part of the name refers to the fact that the fluid substance seen in this type of joint appeared to the old anatomists to be like raw egg white (ovum = egg).

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