- Consists predominantly of contractile cells and produces the movements of various parts of the body by contraction.
- Occurs in three types: skeletal, cardiac and smooth
| Skeletal Muscle |
- Is voluntary and striated; makes up about 40% of the total body mass; and functions to produce movement of the body, generate body heat, and maintain body posture.
- Has two attachments, an origin (which is usually the more fixed and proximal attachment), and an insertion (which is the more movable and distal attachment).
- Is enclosed by epimysium , a thin layer of connective tissue. Smaller bundles of muscle fibers are surrounded by perimysium. Each muscle fiber is enclosed by endomysium.
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| Cardiac Muscle | - Is involuntary and striated and forms the myocardium , the middle layer of the heart.
- Is innervated by the autonomic nervous system but contracts spontaneously without
any nerve supply. - Includes specialized myocardial fibers that form the cardiac conducting system.
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| Smooth Muscle | - Is involuntary and nonstriated, and generally arranged in two layers, circular and longitudinal , in the walls of many visceral organs.
- Is innervated by the autonomic nervous system, regulating the size of the lumen of
a tubular structure. - Undergoes rhythmic contractions called peristaltic waves in the walls of the
gastrointestinal (GI) tract, uterine tubes, ureters, and other organs.
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