The human body is a complex system. It consists of cells or small units that are organized to function together. Every body function is coordinated by the nerve cells in the brain, whether it is movement of the eyes or the heartbeat. In the body, Muscles are one of the most important constituents. They account for 40 percent of body weight. These are the tissues or materials with specialized cells. Muscles are made up of elastic fibers that can contract and relax. The contractile nature of Muscle makes possible various body movements, an upright posture and specific shape to a human body. For example, lifting a box involves the action of Muscles in the hands.

Muscle is the powerhouse of the body. It maintains body temperature as well as supplies energy from the stored glucose. That is, Muscles convert the carbohydrates received from the food to glycogen or glucose. It releases the stored glucose as energy, when a certain body part gets exhausted. Every organ in the body has specific Muscles connected to bones, Muscles and organs to help them perform their functions.

In a human body there are three types of muscles, namely, skeleton Muscles, smooth Muscles and cardiac Muscles. Skeleton Muscles are large Muscles and help the body to move. These Muscles are flexible and voluntary in nature. That is, human beings consciously control their movements. They are technically known as striated Muscles, as they appear striated when viewed under a microscope. Some of the common examples of skeleton or voluntary or striated Muscles are the Muscles in the hands and legs.

Smooth Muscles, on the other hand, are found in the stomach, digestive system, air passage and blood vessels. The third type of muscles, the cardiac Muscles, are found in the heart alone. Unlike the striated muscles, smooth and cardiac are non-striated muscles. These Muscles are involuntary in nature. That is, the movement of non-striated or involuntary muscles, such as the smooth and cardiac Muscles, are guided or automatically controlled by the nervous system.

Muscles are prone to wear and tear. It may happen due to overuse of muscles, Muscle fatigue caused from being in a dormant position, or dehydration caused from excessive loss of body fluids and essential minerals. It may also occur from diseases and an injury that damages certain areas in a muscle. Hence, in order to keep them flexible and in shape, one needs to exercise and practice a routine movement of all the voluntary muscles. There are more than 630 Muscles in a human body, and it is often said that not all Muscles function alike. "It takes 17 Muscles to smile and 42 to frown"!