9 Functions of the Muscular System

Medically reviewed by William A. Morrison, MD on December 13, 2016Written by Annamarya Scaccia on December 13, 2016

What are the main functions of the muscular system?

Muscles play a part in every function of the human body, from circulation to mobility. The muscular system is made up of over 600 muscles. These include three muscle types: smooth, skeletal, and cardiac.

Only skeletal muscles are voluntary, meaning you can control them consciously. Smooth and cardiac muscles act involuntarily.

Each muscle type in the muscular system has a specific purpose. You're able to walk because of your skeletal muscles. You can digest because of your smooth muscles. And your heart beats because of your cardiac muscle.

The different muscle types also work together to make these functions possible. For instance, while you're running (using skeletal muscles), your heart pumps harder (due to the cardiac muscle), which causes you to breathe heavier (using smooth muscles).

Keep reading to learn about some of your muscular system’s main functions.

1. Mobility

mobility

Mobility is your muscular system's simplest and most crucial function. Your skeletal muscles are largely responsible for the movements and motions you make. Skeletal muscles are attached to your bones. They’re controlled, in part, by the central nervous system. You use your skeletal muscles when you bend, twist, stretch, run, and perform other movements. Fast-twitch skeletal muscles cause short bursts of speed and strength, while slow-twitch muscles function better for longer movement.

Try this: 5 joint mobility exercises to improve flexibility and function »

2. Circulation

circulation

The involuntary cardiac and smooth muscles help your heart beat and blood flow through your body. The cardiac muscle, known as the myocardium, is found in the walls of heart. The cardiac muscle is controlled by the autonomic nervous system, which is responsible for most bodily functions.

This muscle produces electrical impulses, which help pump blood and cause your heart to beat. It’s striated, like skeletal muscles, and has one central nucleus, like a smooth muscle. Your blood vessels are made up of smooth muscles, and are also controlled by the autonomic nervous system.

3. Respiration

respiration

Your diaphragm is the main muscle at work during quiet breathing. More labored breathing, like what you experience during exercise, may require accessory muscles to assist the diaphragm. These may include the abdominal, neck, and back muscles.

Learn more: Breathe deeper to improve health and posture »

4. Digestion

digestion

Digestion is controlled by smooth muscles found in your gastrointestinal tract. This comprises the:

  • mouth
  • esophagus
  • stomach
  • small and large intestines
  • rectum
  • anus

The digestive system also includes the liver, pancreas, and gallbladder.

Your smooth muscles contract and relax as food passes through your body during digestion. These muscles also help push food out of your body, whether through defecation or vomiting when you're sick.

Read more: Preventing digestion problems »

5. Urination

urination

Smooth and skeletal muscles make up the urinary system. The urinary system includes your:

  • kidneys
  • bladder
  • ureter
  • urethra
  • penis or vagina
  • prostate

The dome of your bladder is made of smooth muscles. You’re able to release urine when those muscles tighten up. When they relax, you’re able to hold in your urine. But all of the muscles in your urinary system work together so you can urinate.

6. Child birth

child birth

Smooth muscles are also found in the uterus. During pregnancy, these muscles grow and stretch to compensate for the baby's development. When a woman is ready to go into labor, the smooth muscles of the uterus contract and relax to help push the baby through the vagina.

Learn more: Maintaining a healthy pregnancy »

7. Vision

vision

Your eye socket is made up of six skeletal muscles that help you move your eyes. The internal muscles of your eyes, though, are made up of smooth muscles. These muscles work together to help you see the world around you. If these muscles ever become damaged, your vision can become impaired.

8. Stability

stability

The skeletal muscles in your core help with stability and protecting your spine. Your abdominal muscles, back muscles, and pelvic muscles make up your core muscle group. This core muscle group is also known as the trunk. The stronger your core, the better you’re able to stabilize your body. The muscles in your legs also help steady you.

Try this: 5 scapular stabilization exercises for strong shoulders »

9. Posture

posture

Your skeletal muscles also control posture, from your head down to your toes. Flexibility and strength are keys to maintaining proper posture. Stiff neck muscles, weak back muscles, and tight hip muscles, among other ailments, can throw off your alignment. Poor posture can affect your shoulders, spine, hips, and knees. This can lead to joint pain and weaker muscles.

The bottom line

The muscular system is an intricate and complex network of muscles that are vital to the human body. Muscles play a part in everything you do, from chewing to dancing to sleeping. They control our heartbeat and breathing, help our digestion, and allow us to move in the world.

Muscles, like the rest of your body, thrive on exercise and healthy eating. But too much exercise can lead to sore muscles from overuse. Muscle pain can also be a sign that something more serious or chronic is affecting your body.

The following conditions can impact the muscular system and its functions:

  • myopathy (muscle disease)
  • muscular dystrophy
  • multiple sclerosis
  • Parkinson's disease
  • fibromyalgia

It's important to take care of your muscles so they remain healthy and strong. If you have a muscular condition such as muscular dystrophy, speak with your doctor about ways to maintain muscle health and manage your condition.

Keep reading: The 5 best ab exercises for women »

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