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A expansion joint, or movement joint, is an assembly designed to hold parts together while safely absorbing temperature-induced expansion and contraction of building materials. They are commonly found between sections of buildings , bridges , sidewalks , railway tracks , piping systems , ships , and other structures.
Slip joints are common under conditions where temperature changes can cause expansion and contraction that may overstress a structure. These are generally referred to as expansion joints . Bridges and overpasses frequently have sliding joints that allow a deck to move relative to piers or abutments.
Wound contraction, where the edges of the skin are pulled together to close the wound, is a normal part of wound healing. However, large wounds and abnormal wound healing cause skin contractures by excessively tightening the skin and limiting movement. [6] [7] [8] A skin contracture due to a burn is known as a burn scar contracture.
A loss of muscle tone inhibition causes a muscle to become hyperactive resulting in constant contraction, which reduces an individual’s control of the affected area. The joint will remain in a flexed state producing similar effects as listed in immobilization.
Depiction of smooth muscle contraction. Muscle contraction is the activation of tension-generating sites within muscle cells. [1] [2] In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. [1]
The stretch reflex (myotatic reflex), or more accurately "muscle stretch reflex", is a muscle contraction in response to stretching a muscle. The function of the reflex is generally thought to be maintaining the muscle at a constant length but the response is often coordinated across multiple muscles and even joints. [1]
The joint is able to become stiffer and more stable due to this action. [ 4 ] [ 5 ] For example, when the biceps and the triceps coactivate, the elbow becomes more stable. This stabilization mechanism is also important for unexpected loads impeded on the joint, allowing the muscles to quickly coactivate and provide stability to the joint.
Joints can also be classified based on their anatomy or on their biomechanical properties. According to the anatomic classification, joints are subdivided into simple and compound, depending on the number of bones involved, and into complex and combination joints: [19] Simple joint: two articulation surfaces (e.g. shoulder joint, hip joint)