While there is no consensus as to an exact number, most experts agree that the human body has more than 650 muscles. The structure of the muscular system is complex, but generally, muscles are divided into three categories: skeletal, smooth, and cardiac. Some muscles are voluntary, while others are involuntary. Additionally, certain muscles are striated, while others are not.
When most people think of the structure of the muscular system, the skeletal muscles are the ones that come to mind. These are the prominent muscles people build with exercise. They are attached to the bones via tendons and are responsible for voluntary movement. In other words, a person has to consciously think about moving the skeletal muscles in order for action to occur.
The skeletal muscles are striated, which means that, up close, they look as if they have lines running through them. These visible lines are actually indicative of the type of fiber and tissue that make up the muscles. Most skeletal muscles work in pairs, with one muscle responsible for movement in one direction and another in charge of moving in the opposite direction. Similarly, many of them work together in accomplishing one fluid movement. For instance, in order to lift up a glass of iced tea, several groups of muscles have to work in unison to accomplish even such a simple task.
Another group of muscles found within the muscular system are the smooth muscles. As the name suggests, these muscles are not striated but have a smooth appearance instead. They are considered involuntary because a person does not have to think about moving them in order for them to do their jobs. This group of muscles takes care of important bodily functions such as digestion, breathing, swallowing, and blood flow. They can be found in places such as the stomach, blood vessel walls, and respiratory system and are controlled automatically by a particular area of the brain.
The structure of the muscular system also includes the cardiac muscles. This group of muscles is found in the walls of the heart and are responsible for keeping the heart pumping. Like the smooth muscles, they are involuntary so that a person does not have to consciously think about every beat his or her heart takes. They also have a striated appearance, but unlike the skeletal muscles, they are designed to make short, quick contractions rather than broad movements.
Given the extensive structure of the muscular system, about half of a person’s overall weight comes from muscle. Most people are aware of the need to exercise in order to improve the strength and appearance of the voluntary, skeletal muscles. Still, even though the smooth and cardiac muscles are involuntary, they need to be cared for as well. A nutritious diet and a sufficient amount of cardiovascular exercise can improve the tone and function of the muscular system and thus improve a person’s overall health.