Muscular System

Muscular System

There are over 600 muscles in the body. They do everything from pumping blood throughout your body to helping you lift heavy objects. You control some of your muscles, while others (like your heart) do their jobs without your even thinking about them at all. Muscles are the tissues in the body that contract and affect the movement of and within the body. Muscle tissue is classified as striated, smooth, or cardiac, according to its structure and function.

About Muscular System

Striated, or skeletal, muscle forms the bulk of the body's muscle tissue and gives the body its general shape. It is called striated because it appears striped (alternating bands of light and dark) when viewed under a microscope, and there is conscious control over most of their striate muscles.

Smooth muscle, which lines most of the hollow organs of the body, is not under voluntary control, but is regulated by the autonomic nervous system. Smooth muscle fibers are spindle shaped, not striated, and are typically arranged in dense sheets. Smooth muscle lines the blood vessels, hair follicles, urinary tract, digestive tract, and genital tract. Its speed of contraction is slower than that of striated muscle, but it can remain contracted longer.

Cardiac muscle is striated like skeletal muscle but, like smooth muscle it is controlled involuntarily. It is found only in the heart, where it forms that organ's thick walls. The contractions of cardiac muscle are stimulated by a special clump of muscle tissue located on the heart (the pacemaker), although the rate of contractions is subject to regulation by the autonomic nervous system.

One statement that appears frequently in lists of surprising facts states that ''the tongue is the strongest muscle in the body,'' but it is difficult to find any definition of strength that would make this statement true. Note that the tongue consists of sixteen muscles, not one.

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