The human body contains over 600 muscles. They do everything from pumping blood throughout the body to helping a person lift something heavy. A person can control some of their muscles, while others, like the heart muscle, do their jobs without having a person to thinking about them.
Muscles are all made of the same material, a type of elastic tissue resembling a rubber band. There are thousands, or even tens of thousands, of these small fibers that make up each muscle.
There are three different types of muscles in the body: smooth, cardiac, and skeletal.
Smooth muscles which are also called involuntary muscles are usually in sheets, or layers, with one layer of muscle behind the other. A person can't control this type of muscle. The brain and body tell these muscles what to do without a person even thinking about it. Smooth muscles are not used to make a muscle in the arm or jump into the air. Smooth muscles are at work all over the body. In the stomach and digestive system, they contract and relax to allow food to make its journey through the body. Smooth muscles come in handy if a person is sick and needs to throw up. The muscles push the food back out of the stomach so it comes up through the esophagus and out of the mouth.
Smooth muscles are also found in the bladder. When they're relaxed, they allow a person to hold in urine until they can get to the bathroom. They then contract so that urine can be pushed out.
The muscle that makes up the heart is called cardiac muscle. The thick muscles of the heart contract to pump blood out and then relax to let blood back in after it has circulated through the body. Just like smooth muscle, cardiac muscle works all by itself with no help from the person. A special group of cells within the heart are known as the pacemaker of the heart because it controls the heartbeat.
Other muscles are the ones that show how strong a person may be and lets them physically exert the body. These are skeletal muscles which are the voluntary muscles, which mean a person can control what they do. A leg won't bend to kick the soccer ball unless the person causes the muscle to move.
These are the muscles that cover the bones and provide strength and flexibility to the body. Skeletal muscles are held to the bones with the help of tendons and they work as special connector pieces between bone and muscle. The tendons are attached so well that when a muscle is contracted, the tendon and bone move along with it. Skeletal muscles come in many different sizes and shapes to allow them to do many types of jobs. Some of the biggest and most powerful muscles are in the back, near the spine. These muscles help keep a person upright and standing tall.
Whether exerting physical energy to exercise, smiling, frowning, crying, sleeping or are just relaxing, muscles are continuously at work keeping the body functioning. Although there are three categories of muscles and each work independently, they combine to keep the body alive, healthy and in motion.