Human muscle system | Functions, Diagram, & Facts (2024)

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Written by

Shane W. Cummings Contributor to SAGE Publications's Encyclopedia of Sports Medicine (2011). His work for that encyclopedia formed the basis of his contributions to Britannica.

Shane W. Cummings,

Bernard Wood Derby Professor of Anatomy, University of Liverpool. Author of Human Evolution and Evolution of Early Man.

Bernard WoodAll

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human muscle system, the muscles of the human body that work the skeletal system, that are under voluntary control, and that are concerned with movement, posture, and balance. Broadly considered, human muscle—like the muscles of all vertebrates—is often divided into striated muscle (or skeletal muscle), smooth muscle, and cardiac muscle. Smooth muscle is under involuntary control and is found in the walls of blood vessels and of structures such as the urinary bladder, the intestines, and the stomach. Cardiac muscle makes up the mass of the heart and is responsible for the rhythmic contractions of that vital pumping organ; it too is under involuntary control. With very few exceptions, the arrangement of smooth muscle and cardiac muscle in humans is identical to the arrangement found in other vertebrate animals.

This article is concerned with the skeletal muscles of the human body, with emphasis on muscle movements and the changes that have occurred in human skeletal musculature as a result of the long evolutionary process that involved the assumption of upright posture. Smooth muscle and cardiac muscle and the physiology of muscle contraction are treated at great length in the article muscle. For descriptions of disorders that affect the human muscle system, see muscle disease.

The muscle groups and their actions

The following sections provide a basic framework for the understanding of gross human muscular anatomy, with descriptions of the large muscle groups and their actions. The various muscle groups work in a coordinated fashion to control the movements of the human body.

The neck

Britannica QuizFacts You Should Know: The Human Body Quiz

The motion of the neck is described in terms of rotation, flexion, extension, and side bending (i.e., the motion used to touch the ear to the shoulder). The direction of the action can be ipsilateral, which refers to movement in the direction of the contracting muscle, or contralateral, which refers to movement away from the side of the contracting muscle.

Rotation is one of the most-important actions of the cervical (neck) spine. Rotation is accomplished primarily by the sternocleidomastoid muscle, which bends the neck to the ipsilateral side and rotates the neck contralaterally. Together, the sternocleidomastoid muscles on both sides of the neck act to flex the neck and raise the sternum to assist in forced inhalation. The anterior and middle scalene muscles, which also are located at the sides of the neck, act ipsilaterally to rotate the neck, as well as to elevate the first rib. The splenius capitis and splenius cervicis, which are located in the back of the neck, work to rotate the head.

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Side bending also is an important action of the cervical spine. The sternocleidomastoid muscles are involved in cervical side bending. The posterior scalene muscles, located on the lower sides of the neck, ipsilaterally bend the neck to the side and elevate the second rib. The splenius capitis and splenius cervicis also assist in neck side bending. The erector spinae muscles (iliocostalis, longissimus, and spinalis) are large, deep muscles that extend the length of the back. All three act to ipsilaterally side bend the neck.

Neck flexion refers to the motion used to touch the chin to the chest. It is accomplished primarily by the sternocleidomastoid muscles, with assistance from the longus colli and the longus capitis, which are found in the front of the neck. Neck extension is the opposite of flexion and is accomplished by many of the same muscles that are used for other neck movements, including the splenius cervicis, splenius capitis, iliocostalis, longissimus, and spinalis muscles.

The back

The back contains the origins of many of the muscles that are involved in the movement of the neck and shoulders. In addition, the axial skeleton that runs vertically through the back protects the spinal cord, which innervates almost all the muscles in the body.

Multiple muscles in the back function specifically in movements of the back. The erector spinae muscles, for example, extend the back (bend it backward) and side bend the back. The semispinalis dorsi and semispinalis capitis muscles also extend the back. The small muscles of the vertebrae (the multifidi and rotators) help rotate, extend, and side bend the back. The quadratus lumborum muscle in the lower back side bends the lumbar spine and aids in the inspiration of air through its stabilizing affects at its insertion at the 12th rib (the last of the floating ribs). The scapula (shoulder blade) is elevated by the trapezius muscle, which runs from the back of the neck to the middle of the back, by the rhomboid major and rhomboid minor muscles in the upper back, and by the levator scapulae muscle, which runs along the side and back of the neck.

Human muscle system | Functions, Diagram, & Facts (2024)

FAQs

What are the facts and functions of the muscular system? ›

The muscular system is composed of specialized cells called muscle fibers. Their predominant function is contractibility. Muscles, attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction.

What are the 7 major muscles of the body? ›

Major muscles of the body: An overview of the 7 major muscle groups
  • The Trunk Rotators. Your trunk rotators enable you to rotate your spine, simple as that. ...
  • The Trunk Flexors. ...
  • The Trunk Extensors. ...
  • The Lateral Flexion Muscles. ...
  • The Hip Flexors and Adductors. ...
  • The Hip Extensors and Abductors. ...
  • The Shoulders.
Dec 22, 2023

What is the strongest muscle in the human body? ›

If you define strength to mean the ability to exert the most pressure, then the strongest muscle in the human body is the masseter muscle. Of course, you probably call the masseter your jaw muscle. This thick cheek muscle near the back of your jaw opens and closes your mouth when you chew.

What disease affects the muscular system? ›

Types of neuromuscular disorders include:
  • Amyotrophic lateral sclerosis (ALS)
  • Charcot-Marie-Tooth disease.
  • Multiple sclerosis.
  • Muscular dystrophy.
  • Myasthenia gravis.
  • Myopathy.
  • Myositis, including polymyositis and dermatomyositis.
  • Peripheral neuropathy.

What is the largest muscle in the human body? ›

The Gluteus Maximus (GM) muscle is the largest and most powerful in the human body. It plays an important role in optimal functioning of the human movement system as well as athletic performance.

What is the main organ in the muscular system? ›

The human heart is the organ where cardiac muscles are located and are accountable for automatic contractions in the heart.

What is muscle made of? ›

Make-up of muscle

An individual muscle fibre is made up of blocks of proteins called myofibrils, which contain a specialised protein (myoglobin) and molecules to provide the oxygen and energy required for muscle contraction. Each myofibril contains filaments that fold together when given the signal to contract.

What is a fun fact about the human muscles? ›

There are no actual muscles located in your fingers and thumbs. Instead, your digits move by the action of almost 40 muscles located in your forearm and hand. The tendons of these muscles run into the fingers and attach to the bone to move your fingers, much like a rope and pulley system.

Can muscles work without blood? ›

Muscles generate energy from food and oxygen that come through your bloodstream. Muscles use this energy to contract (shorten). The bigger the muscles are and the more blood supply they have, the stronger they can contract. Without a good blood supply, your muscles can't do much work.

What is the most important muscles in the body? ›

The 5 Most Important Muscles You Have
  1. The diaphragm. This “dome” under your rib cage is vital not only for proper breathing function, but also for proper spine stability. ...
  2. Gluteus maximus. ...
  3. Gluteus medius. ...
  4. Lower trapezius. ...
  5. Transverse abdominus.

What is the smallest muscle in the human body? ›

Stapedius muscle is termed to be the smallest skeletal muscle in human body, which has a major role in otology. Stapedius muscle is one of the intratympanic muscles for the regulation of sound.

What is the V muscle called? ›

The Adonis belt is the V-shaped muscle that runs diagonally from your hip bones to the pelvic region. It's made of the inguinal ligament and the transverse abdominis (TVA). It's the deepest core muscle group in your abdomen. The Adonis belt is more visible in certain people.

Is the heart a muscle? ›

Your heart is actually a muscular organ. An organ is a group of tissues that work together to perform a specific function. In the case of your heart, this function is pumping blood throughout your body. Additionally, the heart is largely made up of a type of muscle tissue called cardiac muscle.

What are the 5 functions of the muscular system quizlet? ›

The muscular system helps with body movement, supports body posture, produces heat and energy, protects internal organs, helps make blood, food, and waste products through the body, and opens and closes body openings.

What are the 5 major functions of the skeletal system? ›

The skeletal system is the body system composed of bones and cartilage and performs the following critical functions for the human body:
  • supports the body.
  • facilitates movement.
  • protects internal organs.
  • produces blood cells.
  • stores and releases minerals and fat.
May 17, 2021

What are the 5 major properties of the muscular system? ›

Final answer: The major properties of the muscular system include excitability, contractility, extensibility, elasticity, and thermal generation. These properties allow muscles to respond to stimuli, contract and extend, return to their original form, and generate heat.

What is the basic function of all muscle tissue? ›

Muscle tissue is composed of cells that have the special ability to shorten or contract in order to produce movement of the body parts.

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