Muscles

Almost half the body's weight is muscle.

There are more than 640 muscles in a human body.

Muscles are the part of our body that allow us to move. A skeleton without muscles is useless. Muscles are able to pull (contract) and relax. When they contract, they pull on your skeleton allowing you to move.

Muscles are connected to bones by tough, cord-like tissues called tendons, which allow the muscles to pull on bones.

Humans have three different kinds of muscle:

• Skeletal muscle is attached to bone, mostly in the legs, arms, abdomen, chest, neck, and face. These muscles hold the skeleton together, give the body shape, and help it with everyday movements (they are known as voluntary muscles because you can control their movement).
• Smooth, or involuntary, muscle. Examples of smooth muscles are the walls of the stomach and intestines, which help break up food and move it through the digestive system. Smooth muscle is also found in the walls of blood vessels, where it squeezes the stream of blood flowing through the vessels to help maintain blood pressure.
• Cardiac muscle is found in the heart. The walls of the heart's chambers are composed almost entirely of muscle fibers. Cardiac muscle is also an involuntary type of muscle. Its rhythmic, powerful contractions force blood out of the heart as it beats.

Picture of leg muscles

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