Muscle

Muscle (from Latin musculus, diminutive of mus "mouse") is the contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to produce force and cause motion. Muscles can cause either locomotion of the organism itself or movement of internal organs. Cardiac and smooth muscle contraction occurs without conscious thought and is necessary for survival. Examples are the contraction of the heart and peristalsis which pushes food through the digestive system. Voluntary contraction of the skeletal muscles is used to move the body and can be finely controlled. Examples are movements of the eye, or gross movements like the quadriceps muscle of the thigh. There are two broad types of voluntary muscle fibers: slow twitch and fast twitch. Slow twitch fibers contract for long periods of time but with little force while fast twitch fibers contract quickly and powerfully but fatigue very rapidly.

Muscular tissue

Wat is muscle?

Specialised cells whose primary function is contraction characterize muscular tissue. These cells, called muscle fibres, are elongated and arranged in parallel arrays. Their coordinated contraction results in movement. Muscular tissue may be classified based on appearance and location. Striated muscle exhibits cross-striations visible under the microscope, while smooth muscle does not. Striated muscle may be further divided into skeletal muscle and cardiac muscle. Skeletal muscle is, for obvious reasons, under voluntary nervous control and is often referred to as voluntary muscle. Smooth muscle is under autonomic nervous control and is largely restricted to the viscera and blood vessels.