In this topic you will learn about how the muscles in your body work.

Bones cannot move on their own. It is the job of the muscles to move bones. The muscles that are attached to a bone and allow movement are called skeletal muscles. Skeletal muscles pull bones to move them. Muscles do not push bones. Most muscles work in pairs to move bones.

A strong band of tissue called a tendon connects a muscle to a bone. Look at the back of your hand. Wiggle the fingers up and down. Do you see the narrow bands running from your fingers to your arm? They are the tendons. These tendons run from muscles in your arm to your fingers.

Three types of muscles make up your body. Besides the skeletal muscles there are cardiac muscles and smooth muscles. Cardiac muscle is the type of muscle that makes up the heart. The heart is a hollow organ made up of four parts, or chambers. The walls of the heart are made of strong cardiac muscle. When your cardiac muscle contracts, it squeezes blood out of your heart. The blood delivers oxygen and nutrients to your cells. It also picks up and carries away the wastes your cells must get rid of. When your cardiac muscle relaxes, your heart fills with more blood.

Smooth muscle makes up the internal organs and blood vessels. Smooth muscles are not attached to bones. They help other body parts do their jobs. There is smooth muscle in the stomach and intestines.

Muscles can be classified by how they are controlled. Cardiac and smooth muscles are involuntary muscles. An involuntary muscle causes movements you cannot control. Most skeletal muscles are voluntary muscles. Voluntary muscles cause movements you can control. Some muscles are both voluntary and involuntary. One example is the large flat muscle under your lungs. All of your muscles together make up your muscular system.

You can take care of your muscles by exercising, eating the right foods, getting plenty of rest, and not taking steroids unless your doctor tells you to.