The Muscular System

This lesson introduces the anatomy of the muscular system, including the three different muscle tissues. This lesson also describes the role of the muscular system in movement and the physiology of muscle contraction.

Anatomy of the Muscle


The muscular system is responsible for all types of body movement. Additional functions of this system include providing support, stabilizing joints, and generating heat for the body. All muscles consist of specialized cells known as muscle fibers, which contract to facilitate body movement. For the body to move, muscles must be attached to bones. Muscles are also attached to internal organs and blood vessels. Thus, most of the body’s movements occur because of muscle contraction from muscle fibers.


Did You Know?

There are over 600 muscles in the body. Muscles are grouped according to characteristics such as size, shape, and location.


The body is comprised of three types of muscles: cardiac, smooth, and skeletal. As shown in the image below, these muscles look different. They also perform different functions.

  • Cardiac muscle: This muscle consists of muscle cells that are striated, short, and branched. These cells contain one nucleus, are branched, and are rectangular. Cardiac muscle contraction is an involuntary process, which is why it is under the control of the autonomic nervous system. This muscle is found in the walls of the heart.
  • Skeletal muscle: This muscle cell is striated, long, and cylindrical. There are many nuclei in a skeletal muscle cell. Attached to bones in the body, skeletal muscle contracts voluntarily, meaning that it is under conscious control.
  • Smooth muscle: This muscle consists of non-striated muscle cells that are spindle-shaped. Like cardiac muscle cells, smooth muscle cells contain one nucleus. This muscle type is found in the walls of internal organs like the bladder and stomach. Smooth muscle contraction is involuntary and controlled by the autonomic nervous system.

Despite the differences among cardiac, smooth, and skeletal muscles, they share four properties: excitability, contractility (muscle shortening), extensibility (muscle stretching), and elasticity.


Be Careful!

Skeletal muscles are excited by the nervous system. Cardiac and smooth muscles are stimulated by the nervous system and by circulating hormones.


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