The Muscular System

Anterior view of major human musclesGroups of muscles in the human body form the muscular system and because many of these muscles are attached to bones, this system is often referred to, along with the skeletal system, as the musculoskeletal system.

There are 639 muscles in the human body which fall into one of three categories – striated, smooth, and cardiac.

Striated muscles are the skeletal muscles such as the ones in the arms, legs, back, and chest.

Smooth muscles are the involuntary muscles and are found in the cardiovascular, digestive, and urinary systems. For instance, the walls of blood vessels contain smooth muscle as do the bladder and intestines.

While the function of the heart muscle is to pump blood to and from the heart and the rest of the body, the purpose of skeletal muscles is to provide movement, posture, balance, strength, and body heat.

drawing of heart and muscle fibersMuscle activity in the human body is actually controlled by the nervous system. The central nervous system directs the movement of involuntary muscles and some reflexes are initiated in the spinal cord. Movement of voluntary skeletal muscles are controlled by the brain and the nervous system.

There are five major muscle groups that help form the musculoskeletal system.

  1. Arms and Shoulders (biceps, triceps, forearm, and deltoids)
  2. Legs (quadriceps, hamstrings, calves)
  3. Abdominals (stomach muscles)
  4. Back (trapezius)
  5. Chest (pectoralis major)
Balance among the different muscles and muscle groups is important in the prevention of pain and injuries and the maintenance of strength and posture. For instance, the right and left hamstrings should be similar in size and strength. Also, the size and strength of opposing muscles such as the biceps and triceps should also be as balanced as possible.