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Jan 23, 2024 · Learn about the different types of muscles in your body, how they work and what can go wrong. Find out how to prevent and treat muscle injuries and disorders with Cleveland Clinic experts.
- Overview
- The muscle groups and their actions
- The neck
- The back
- GeneratedCaptionsTabForHeroSec
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 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.
Britannica 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 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.
Learn about the skeletal muscles of the human body that work the skeletal system and are under voluntary control. Explore the muscle groups and their actions, the evolution of human musculature, and the disorders that affect the muscle system.
Jan 21, 2018 · Learn about the three types of muscle tissue: skeletal, cardiac, and smooth. Find out how muscles work, what problems can affect them, and how to keep them healthy.
Learn about the three types of muscle tissue, how they attach and move bones, and how they are controlled by the nervous system. Explore the common muscular pathologies and their symptoms and treatments.
- Mobility. The muscular system’s main function is to allow movement. When muscles contract, they contribute to gross and fine movement. Gross movement refers to large, coordinated motions and includes
- Stability. Muscle tendons stretch over joints and contribute to joint stability. Muscle tendons in the knee joint and the shoulder joint are crucial in stabilization.
- Posture. Skeletal muscles help keep the body in the correct position when someone is sitting or standing. This is known as posture. Good posture relies on strong, flexible muscles.
- Circulation. The heart is a muscle that pumps blood throughout the body. The movement of the heart is outside of conscious control, and it contracts automatically when stimulated by electrical signals.
Oct 30, 2023 · Learn about the different types of muscle tissue in the human body, their structure, functions and clinical correlations. Explore skeletal, cardiac and smooth muscle, as well as their connective tissues and sarcomeres.
5 days ago · The muscular system is responsible for the movement of the human body. Attached to the bones of the skeletal system are about 700 named muscles that make up roughly half of a person's body weight. Each of these muscles is a discrete organ constructed of skeletal muscle tissue, blood vessels, tendons, and nerves.
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