Muscular System: Function, Parts, and Main Organs

2.4.2025 0 comments

Author: Trisha Houghton

How much do you know about your muscular system?

You’re likely aware that your muscles facilitate activity, or that lifting weights makes your muscles grow. You also know overexertion can lead to muscle pain.

But that’s barely scratching the surface of your entire muscle system function!

In this blog post, we’re going to take a deep dive into the human muscles system.

Well examine its overall role in your daily life, as well as the various muscular system parts. We’ll also look at some of the more common muscular system disorders that can impair your movement and affect your longevity.

But keep reading to the end, because we’ll share a lot of good information on how maintaining your muscular system can ensure efficient movement for years—and even decades—to come.

YourIntroduction to the Muscular System

Let’s start off with the basics: what is the muscular system and what role does it play in my body?

At its simplest, the muscular system serves to facilitate movement and maintain an upright posture. There are a number of other functions (which we’ll explore below), but these are the two most crucial functions to understand.

Think about it: your skeleton is made up of a lot of incredibly sturdy bones connected by joints, but neither bones nor joints actually move. It’s muscles that do the actual movement through contraction and extension.

Because of your muscles, you can run, jump, stand, sit, and play.

Primary Functions of the Muscular System

The two primary functions of the muscular system are movement and posture.

Movement 

Muscles are essentially strands of soft tissue that connect (via tendons) to your bones in order to facilitate movement.

They provide conscious control of voluntary movement, such as raising your hand to scratch your nose or standing up, and involuntary movement, such as your heartbeat or the motion of your back and ribs during breathing.

Muscles are essential for almost every movement in the body.

They control not only movements of the torso, limbs, head, and neck but also functions such as:

• Vision (contraction and expansion of muscles in your eyes)
• Hearing
• Breathing
• Speaking
• Swallowing
• Digesting food
• Excreting waste matter
• Giving birth
• Pumping blood

Simply put: without muscles, your body would be a static, unmoving structure of bones, joints, nerves, and organs. It’s muscles that enable you to move.

Posture 

Muscles also play a role in maintaining your posture, keeping you upright and balanced.

They keep your spine aligned from your head to your tail, and control your limbs to maintain your balance as you walk, sit, stand, throw, catch, and move in any way.

Other Functions of the Muscular System

The muscular system also serves a few other important functions:

• Heat production – Muscles are your body’s primary heat source. As muscles work (contract and relax), this activity leads to the breakdown of ATP (turning it into inorganic phosphate and ADP), and this breakdown process leads to the release of both energy (to power your muscles) and body heat. That’s why your body feels warm when you exercise—it’s generating heat as well as energy. Muscles help to control your body temperature.
• Circulation – The muscles in your heart are what cause your heart to “beat”, essentially expand and contract the chambers in your heart that pull blood into or push blood out of your heart. The smooth muscles in your blood vessels also facilitate the movement of blood and fluids.
• Respiration – Your muscles cause your lungs to expand and contract when you inhale and exhale, facilitating the absorption of oxygen and the expulsion of carbon dioxide.
• Digestion and Elimination – Muscles along your stomach and intestines ensure the food and liquids you consume move through your digestive tract, where they can be absorbed into the body or eliminated as waste.

There’s no two ways about it: your muscles are incredibly important for your health, wellbeing, and daily activities of life.

Types of Muscle Tissue

There are three types of muscle tissues in the human body.

Skeletal Muscle 

Skeletal muscles (also called striated muscle tissue) attach to your skeletal system (aka, your bones) in order to facilitate movement. In partnership with your bones, ligaments, and tendons, they also help support your weightwhile you move.

Skeletal muscles tend to be voluntary, meaning they respond to your conscious signals to move rather than contracting/lengthening on their own.

Smooth Muscle

Smooth muscles (also called visceral muscle) line your internal organs, including your stomach, intestines, and lungs.

They are involuntary muscles (controlled directly by signals from your brain without you needing to be conscious of it) and play a significant role in digestion, reproduction, waste excretion, and respiration.

Cardiac Muscle 

Cardiac muscle is found only in your heart. It’s an involuntary muscle responsible for the contraction and expansion of your heart to pump blood.

Cardiac muscle stimulates your heart beat and keeps your blood flowing. A unique feature of cardiac muscle is that it contains intercalated discs that ensure synchronized contraction for effective blood pumping.

Main Parts of the Muscular System

The muscular system has a lot of moving parts (yes, pun intended) and can be very complex, but let’s break it down so it’s a bit easier to understand.

First off, there are the muscle groups. 

There are more than 600 muscles in the body (way too many for us to list here), but you can form them into a few “groups” based on the body parts they’re attached to or the limbs they help move.

(Note: We’ll dive into the muscle groups in more detail in a section below…)

But your muscles can’t work alone. They have to be connected to something else—namely, your bones, the other half of your musculoskeletal system—in order to facilitate movements.

The muscle tendons are responsible for connecting your muscles to your bones, while muscle ligaments connect your bones to each other. Both are tough bands of tissue that provide joint stability.

Together with the joints and connective tissues, your muscles maintain posture and facilitate precise movements of your skeletal structure.

There are two other muscles considered part of the muscular system:

• The diaphragm, a dome-shaped muscle that facilitates inhalation and exhalation, aka breathing. The muscle relaxes to allow you to breathe out, then contracts to cause you to breathe in.
• The heart, which is formed of cardiac muscle. The contraction and relaxation of your cardiac muscle is what pumps blood through your body to maintain healthy circulation.

All together, these four muscle types work together to facilitate movement in every part of your body.

How the Muscular System Works

We’ve talked a lot about what the muscular system is and what it does, but now it’s time to dive into the how.

Let’s break it down to a step-by-step so you understand the exact process of muscles contracting and relaxing to facilitate movement:

Step 1: Signal Transmission

Your brain sends signals through the nervous system to your muscles. These signals can be voluntary, such as deciding to stand up or sit down, or involuntary, like maintaining your heartbeat.

Electrical signals race through your somatic system and to your motor neurons.

Step 2: Muscle Fiber Activation

The electrical signal excites your motor neurons, which in turn activate smooth, cardiac, or skeletal muscle fibers.

This process triggers the individual muscle fibers to prepare for contraction.

Step 3: Muscle Contraction

The activated smooth, cardiac, or skeletal muscle tissue does what its programmed to do, contract. 

Muscle contraction happens when actin and myosin filaments slide past each other, shortening the muscle fibers. This process uses ATP for energy.

The ATP that is bound to myosin is turned into adenosine diphosphate (ADP) and an inorganic phosphate molecule, both of which stay connected to the myosin. In its new “cocked” position, myosin binds itself to a new site on the actin, creating a power stroke that pulls the actin filaments.

Myosin filaments pull on the actin filaments, which are attached to Z discs at the end of sarcomeres. Pulling the Z discs closer together shortens the sarcomere, thereby shortening the muscles—what we call contracting muscle.

This all seems complicated. However, like so many other internal functions, it happens incredibly fast—in microseconds. We only see the end result: movement.

How Muscles Contraction Work

There are two ways the muscles contract:

• Isotonic contraction, which involves shortening during contraction. You’ll see this when you lift weights, for example. When you curl a barbell to your chest, you’ll see the biceps muscles in your arms shortening. This is an isotonic contraction.
• Isometric contraction, which involves contraction without shortening. You’ll see this when you hold a plank position, for example. Your muscles have to contract to support your weight, but because your arms are at full extension, they don’t contract but remain the same length. This is an isometric contraction.

Both contractions generate the force needed to move your body or support your weight.

Muscle Groups and Their Functions

The main muscle groups are the following:

• Your neck muscles, which includes the sternocleidomastoid, scalene, splenius capitis, splenius cervicis, erector spinae, longus colli, and the longus capitis muscles among others. These are the muscles responsible for rotating your head or tilting it side to side.
• Your chest muscles, which include the pectoralis major, pectoralis minor, serratus anterior, and subclavius, all located in your chest cavity. They play a role in pushing, moving your arms, and rotating your shoulders.
• Your back muscles, which includes all the erector spinae muscles, semispinalis dorsi, semispinalis capitis, quadratus lumborum, trapezius, rhomboid major, and rhomboid minor muscles among others. These muscles play a role in stabilizing your spine, but are also involved in moving your arms, rotating your shoulders, and even moving your lower body.
• Your shoulder muscles and arm muscles, which include the deltoid, triceps, pectoralis major, latissimus dorsi, teres major, coracobrachialis, infraspinatus, biceps brachii, brachialis, flexor compartment, pronator teres, and flexor muscles among others. These muscles raise, lower, bend, extend, push, pull, and rotate your hands, wrists, arms, and shoulders.
• Your abdominal muscles, which includes the rectus abdominis, transversus abdominis,internal oblique, and external oblique among others. Abdominal muscles protect internal organs and assist in breathing by supporting the diaphragm during respiration. The same muscles that play a primary role in maintaining your posture also allow you to bend forward and sideways and twist side to side at the waist.
• Your hip muscles, which include the sartorius, rectus femoris, pectineus, gracilis tiliopsoas, the posterior thigh, gluteus maximus, biceps femoris, semitendinosus, and the semimembranosus among others. These muscles control the movement of your legs and work with your core muscles to maintain solid trunk stability.
• Your leg muscles and feet muscles, which include the quadriceps femoris, hamstring, gastrocnemius, tibialis anterior, extensor digitorum longus, extensor hallucis longus, and soleus among many muscles more. These muscles raise, lower, bend, extend, push, pull, and rotate your legs, ankles, and feet. Leg and foot muscles stabilize posture and provide propulsion for walking, running, and jumping.

The human body is made up of 639 muscles, too many to list here. However, the ones we shared above are the most important to name.

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Common Muscular System Disorders

There are a lot of disorders that can affect the muscular system, so many that we don’t have time to list them all. But we will focus on what are the five most common problems that can impact muscular system function.

Muscle strain 

Muscle strain results when muscle tissue gets stretched to an excess, which leads to a tear in the muscle fibers.

Common causes of muscle strains include accidents and impacts, overusing or overloading a muscle (such as during weightlifting), or using a muscle incorrectly. The damage may be caused directly to the muscle tissue or the tendon that connects it to the bone.

This injury is very common among athletes, resistance trainees, and anyone who engages frequently in high-impact, high-intensity exercise.

Muscular dystrophy 

Muscular dystrophy isn’t just one disorder, but a group of them, all of which cause progressive weakening of your skeletal muscles, as well as muscle mass loss.

Types of muscular dystrophy include Becker, Duchenne type (the most common form in children), Myotonic, Facioscapulohumeral (FSHD), Congenital, and Limb-girdle muscular dystrophy.

Symptoms may include:

• A waddling gait;
• Large calf muscles;
• Frequent falls;
• Delayed growth;
• Muscle stiffness and pain;
• Difficulties jumping and running;
• Difficulty rising from a prone position.

Muscular dystrophy is a genetic mutation that affects the genes that control the production of proteins needed to maintain and repair muscle fibers.

Tendinitis 

Tendinitis is inflammation in the tendons, the connective tissue that links your muscles to your bones.

Common types include:

• Golfer’s elbow;
• Tennis elbow;
• Achilles tendinitis;
• Patellar tendinitis.

Symptoms include mild swelling, pain or aches in the joints, and tenderness.

Tendinitis can be caused either by sudden injury, but it is more commonly the result of repeated motions that puts stress on and ultimately damages the tendons over time.

Fibromyalgia 

Fibromyalgia is a chronic condition that causes pain in your soft tissue (including muscle tissue) all over your body—your arms, legs, neck, shoulders, chest, back, hips, and buttocks.

Fibromyalgia is associated with central nervous system abnormalities, leading to increased pain sensitivity.

The cause of fibromyalgia is still unknown, though it’s believed to be linked to biochemical, endocrine, or immune problems.

Myasthenia Gravis 

Myasthenia Gravis (or MG) is an autoimmune condition where your body’s own antibodies attack and destroy the communication between your nervous system and your muscles. This leads to weakness in your skeletal muscles, as well as the muscles that control your throat, mouth, and eyes.

Symptoms include:

• Fatigue;
• Muscle weakness;
• Visual problems;
• Swallowing difficulties;
• Trouble pronouncing words;
• Weakness in the limbs and/or neck.

The cause is unknown.

Maintaining Muscular System Health

By now, we’ve seen just how important your muscular system is. It should be very clear why it’s essential to keep it healthy and functioning at optimum capacity.

Thankfully, there are a few simple things you can do every day to maintain muscle mass, strength, mobility, and reduce injury risk:

Exercise daily

Exercise benefits your muscles in so many ways:

• Increases muscular strength and size;
• Speeds up muscular metabolism;
• Improves muscle contractile function;
• Facilitates smooth movements of your joints;
• Strengthens the bones that your muscles contract and lengthen to move;
• Strengthen the muscles that control your posture and balance;
• Stave off age-related muscle wasting and protect against muscle mass loss.

You should ideally do at least 3-4 resistance training (weightlifting) workouts a week, along with 2-4 aerobic workouts (high impact and/or low impact) to maintain healthy musculature.

Eat right

Feed your muscles by consuming the following nutrients:

• Protein, which is turned into ATP energy that provides power to your muscles;
• Calcium, which is crucial for muscle contraction;
• Zinc, necessary for turning protein into ATP energy;
• Vitamin C, which is needed to produce the collagen that maintains the integrity of your muscles (and bones and joints);
• Selenium, which protects your muscles against oxidative damage;
• Vitamin D, which optimizes both muscular performance and muscle strength;
• Magnesium, which prevents cramps, aids in muscle relaxation, and facilitates protein formation.

Eat more of these foods to keep your muscles healthy and strong!

Hydrate

Your muscles are about 75% water!

Water carries excess heat away from your muscles during exercise, delivers oxygen and nutrients, flushes out lactic acid (the waste produced by muscle contractions), controls muscle contraction speed, and plays a role in the electrolyte exchange and nerve stimulation that causes muscle contractions.

Electrolytes like sodium and potassium are crucial for muscle contraction and preventing cramps.

Drink at least 3 liters of water per day—though aim for 4-5 if possible.

Rest and recover

Give your muscles at least a 48 hour break between intense physical activity, or 72 hours if you’re training with very heavy loads. It takes about 48 hours (minimum) for your muscles to fully repair and recover following an intense workout.

Failing to rest could lead to injuries like muscle strains.

Protect your mobility

Stretch daily to maintain elasticity in your muscles and protect your joints’ range of motion. Make it a point to spend at least 10-20 per day (morning and night, if you can) stretching.

Wrapping Up

Isnt it amazing just how important the muscular system is?

It’s necessary for not just movement, but posture, balance, stability, heat generation, digestion, and circulation.

Without our muscles, our bodies would be unable to move or function properly.

For this reason, it’s so critical that you take steps to protect your muscular system through the strategies we mentioned above: exercise, a nutrient-rich diet, hydration, rest, and stretching.

Do that, and you’ll keep your muscles strong and functioning at optimum capacity for many more active years to come!

Frequently Asked Questions

What is the strongest muscle in your body? 

The masseter, or jaw muscle, located at the back of your cheek and responsible for chewing and opening your mouth, is the muscle capable of exerting the most force—aka, the strongest.

What is the biggest muscle in the body? 

The gluteus maximus, or buttocks muscle, is the largest muscle in the human body (followed by quadriceps, latissimus dorsi, and hamstring muscles).

What happens to the muscles when they are not often used? 

Lack of use leads to muscular atrophy, or shrinking, as well as loss of strength. Your body breaks down inactive muscle to turn into energy. Inactivity, injury, illness, and aging can all cause muscular atrophy and muscle weakening.

Resources

Introduction to the Muscular System

Human Muscle System

Physiology, Skeletal Muscle

Anatomy, Skeletal Muscle

Introduction to the Muscular System

Muscle Contraction

Muscular dystrophy

Tendinitis

Fibromyalgia

Myasthenia Gravis

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