Types of Muscle Tissue
The three types of muscle are skeletal, smooth, and cardiac. The bulk of the muscle in the body is skeletal muscle, and it is responsible for producing the voluntary movements of the limbs, trunk, and head.
It is also the muscle tissue with which we are most familiar as the meat of our domestic animals. The muscle cells (fibers) of skeletal muscle tissue are grouped into distinct organs of variable size identified as individual muscles. These are usually attached to the bones of the skeleton (hence the term skeletal muscle) and are under voluntary control of the animal. Under the microscope, skeletal muscle fibers exhibit a characteristic striped pattern arising from the orderly arrangement of the contractile proteins within the cells (see Chapter 1, Plate I, No. 11). As a consequence, skeletal muscle is also called striated muscle.Smooth (involuntary or unstriated) muscle is composed of muscle cells that have no striations visible with a microscope. smooth muscle is found in systems of the body with autonomic function. Thus, smooth muscle is a major component of the wall of organs of the digestive and urogenital systems and most blood vessels. Contraction of smooth muscle is an intrinsic property of the fibers themselves, which means that contraction does not generally require stimulation by a nerve; however, the contractility of smooth muscle is regulated and coordinated by the autonomic nervous system.
Cardiac muscle is characterized by fibers with visible striations, so it is considered a type of striated muscle. However, cardiac muscle, like smooth muscle, contracts intrinsically and is not under voluntary control. Cardiac muscle is restricted to the heart, where it constitutes most of the thickness of the wall. its rhythmic contraction is responsible for the circulation of blood.