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The human body is comprised of hundreds of muscles, about 640 in total. There is no exact count largely because expert opinions are conflicted regarding what constitutes a distinct muscle. Therefore, some experts will suggest 639 total while others may suggest there are more. Muscles are found within the muscular system, which is the body’s own network of tissues and fibers responsible for both outward and inward movements of the body.
While the exact number in the human body may not be known, what is known is that muscles are categorized as one of three different types: striated, smooth, and cardiac.
Striated muscles, also called voluntary or skeletal muscles, are those the body has conscious control of. These include those in the face and those that move all the bones of the body. Striated muscles are made of light and dark bands called fibrils. They are the ones typically injured in sports or during physical activity.
Smooth muscles are known as involuntary or visceral muscles, and are controlled by the autonomic nervous system. They differ in appearance from striated and lack the bundles of fiber and patterned fibrils found in striated muscles. They move internal organs, including the digestive tract and secretory glands, and cannot be made to work by conscious effort.
Cardiac muscles are those that make up the heart. Though similar to striated in appearance, cardiac are also involuntary. They work together to pump blood to and from the heart and throughout the body.
Muscles are able to contract, or pull, and are typically paired together in sets that work in conjunction with one another. They come in various sizes and perform many different functions. The busiest are found in the eye and are responsible for blinking, which occurs involuntarily, though can be a voluntary action, approximately 100,000 times each day. The smallest in the human body is located deep inside the ear and called the stapedius. The largest in the human body is the gluteus maximus, or buttock.