Joint, in anatomy, a structure that separates 2 or a lot of adjacent parts of the skeleton. Depending on the sort of joint, such separated parts might or might not locomote each other. This article discusses the joints of the human body—particularly their structure however additionally their ligaments, nerve and blood supply, and nutrition. Although the discussion focuses on human joints, its content is applicable to joints of vertebrates in general and mammals in particular. For data concerning the disorders and injuries that usually have an effect on human joints, see joint disease.
Types of Joints
Joints can be classified in two ways: temporally and structurally. Each classification is associated with joint function.
Considered temporally, joints are either transient or permanent. The bones of a transient joint fuse together sooner or later, but always after birth. The bones of a permanent joint do not fuse except as the result of disease or surgery. Such fusion is called arthrodesis. All permanent and some transient joints permit movement.
There are 2 basic structural kinds of joint: synovial joint, in which fluid is present, and synarthrosis, in which there is no fluid.All the diarthroses (commonly known as secretion joints) are permanent.Some of the synarthroses are transient while other synarthroses are permanent.
Here are some types:
In order to explain the main kinds of joint structures, it is helpful first to summarize the motions made possible by joints. These motions include spinning, swinging, gliding, rolling, and approximation.
Spin is a movement of a bone around its own long axis; it’s denoted by the anatomical term rotation. When Person presses the rear of the hand against the mouth, the forearm is pronated, or twisted; when the palm of the hand is pressed against the mouth, the forearm is supinated, or untwisted. Pronation is caused by medial (inward) rotation of the radius and supination by lateral (outward) rotation.
Swing, or angular movement, brings a change in the angle between the long axis of the moving bone and reference line in the bone which is fixed. Flexion (bending) and extension (straightening) of the elbow are examples of swing. A swing (to the right or left) of one bone away from another is called abduction; the reverse, adduction.
Approximation denotes the movement caused by pressing or pulling one bone directly toward another—i.e., by a “translation” in the physical sense. The reverse of approximation is separation. Gliding and rolling movements occur solely among secretion joints and cause a moving bone to swing.