How Many Muscles Does a Human Have?

What we think of as a muscle is actually layers upon layers of muscular tissue, so coming up with a single number would be difficult. But we humans are definitely muscle bound. Muscular tissue makes up 35-40 percent of our body weight and comes in several types of packages—skeletal, cardiac and smooth.

Skeletal muscles consist of about 650 striated layers connected to bones, so that's a figure often cited. The muscles you admire on Mr. and Ms. Universe (biceps, abdominals and the like) are the voluntary skeletal muscles, whose movements are controlled consciously by the prefrontal and motor cortex in the brain.

Most skeletal muscles are voluntary, but some others are involuntary—controlled not by our gray matter but by the peripheral nervous system. These control everything from the eye's iris to swallowing to goose bumps. In addition, cardiac muscles work the heart tirelessly and smooth muscles control the movements of our other internal organs.

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