The muscles of the body that are attached to the skeleton. These muscles are responsible for voluntary movement, and also support and stabilize the skeleton. In most cases, a muscle attaches to a bone (usually by means of a tendon) and crosses over a joint to attach to another bone. Muscles can produce movement by contracting and shortening to pull on the bone to which they are attached. They can only pull, not push, and are therefore arranged so that the pull of one muscle or group of muscles is opposed to another, enabling a movement to be reversed. Although most actions of the skeletal muscles are under conscious control, reflex movements of certain muscles occur in response to stimuli. There are more than 600 muscles in the body, classified according to the type of movement they produce. An extensor opens out a joint, a flexor closes it; an adductor draws a part of the body inwards, an abductor moves it outwards; a levator raises it, a depressor lowers it; and constrictor or sphincter muscles surround and close orifices.
Muscular system |
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