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  1. Innerbody Anatomy Explorer. There are 12 major anatomy systems: Skeletal, Muscular, Cardiovascular, Digestive, Endocrine, Nervous, Respiratory, Immune/Lymphatic, Urinary, Female Reproductive, Male Reproductive, Integumentary. Select a system below to get started.

    • Muscular

      The Muscular System. Learn about the three types of muscle...

    • Cardiovascular

      The cardiovascular system consists of the heart, blood...

    • Digestive

      The liver weighs about 3 pounds and is the second largest...

    • Endocrine System

      Anatomy of the Endocrine System ... Testosterone has effects...

    • Respiratory

      The cells of the human body require a constant stream of...

  2. Jan 21, 2018 · muscular system. Muscular. The primary job of muscles is to move the bones of the skeleton, but muscles also enable the heart to beat and constitute the walls of other vital hollow organs....

    • Overview
    • The muscle groups and their actions
    • The neck
    • The back

    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.

    • Skeletal system. The skeletal system is composed of bones and cartilages. There are two parts of the skeleton; axial and appendicular. The axial skeleton consists of the bones of the head and trunk.
    • Muscular system. The muscular system consists of all the body muscles. There are three muscle types; smooth, cardiac and skeletal muscles. Smooth muscle is found within walls of blood vessels and hollow organs such as the stomach or intestines.
    • Cardiovascular system. The cardiovascular system is comprised of the heart and the circulatory system of blood vessels. The heart is composed of four chambers; two atria and two ventricles.
    • Respiratory system. The respiratory system consists of a series of organs; the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles and lungs (alveoli).
  3. Zygote Body is a free online 3D anatomy atlas. View, isolate, and learn human anatomy structures with Zygote Body.

  4. 5 Facts about Human Muscles: An Overview of Muscles and How They Move. What do the muscles throughout the body do? At the simplest level, muscles allow us to move. Smooth muscle and cardiac muscle move to facilitate body functions like heartbeats and digestion.

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