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Welcome to the Visible Body Blog! Learn Muscle Anatomy: Sternocleidomastoid. Actions of the Sternocleidomastoid The SCM's main responsibility is moving the vertebral column and head.
Sternocleidomastoid Injuries Since the SCM is involved in so many actions, it stands to reason that it would be just as susceptible to injury. Subscribe Here! Most Popular. Get our awesome anatomy emails! About News Contact. All Rights Reserved. User Agreement Privacy Permissions. Upper part of the anterior surface of manubrium.
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Login Register. Additional recommended knowledge. Topics A-Z. All topics. To top. About bionity. Your browser is not current. The sternocleidomastoid is a superficially located neck muscle that plays an important role in tilting your head and turning your neck, as well as other things. It courses from the back of your head and attaches to your breastbone and collar bone.
The sternocleidomastoid, often referred to as the SCM, is usually quite easy to see. Visually, it appears as a cylindrical, strap-like shape that emerges from the side of your neck and tapers at the ends. The sternocleidomastoid runs diagonally from the back of the ear to both the collarbone and the breastbone.
Unlike other muscles such as the latissimus dorsi , a large muscle in your back, the points of attachment for the SCM muscle are relatively simple to identify and follow.
In contrast, to the lats, the SCM only attaches to bones, and to a total of just four bones, at that. So from where, exactly, are these two "heads" of the SCM? One attaches on the front i. The manubrium is uppermost section of the breastbone.
The other head attaches on the top part called superior aspect of the collarbone , near the midline of the body. The other end of the SCM inserts on the mastoid process, a little projection of bone located behind your ear.
You can identify your mastoid process yourself by touching the area behind, and a little below, your ear. Then, if you walk your fingers down a bit you may feel a softer area. That is where the SCM attaches to the mastoid bone. A few fibers of the SCM also insert on the bottom of the occipital bone, which is located right next to the mastoid process, and forms, again, the bottom of, the skull. The SCM muscle is of interest to anatomists because the unique position it occupies in the neck makes it key to understanding the layout of cervical muscles.
On either side, the SCM diagonally divides the neck musculature into anterior front and posterior back triangles, making the cervical spine easier to study. The sternocleidomastoid muscle is innervated by the accessory nerve. In part, the neck movements produced by the sterocleiomastoid vary depending on whether one or both of the SCM muscles are working.
When just one SCM muscle contracts, it tilts your head to the same side called the ipsilateral side to which the muscle is located. For example, the SCM on the right side of your neck tilts your head to your right.
One SCM can also turn, or rotate, your head to the opposite side. For example, when you rotate or turn your head to the right, your left SCM is contracting. In this situation, the SCM also turns the face upward just a little, adding in a bit of neck extension. When both SCM muscles contract, the result is a neck extension movement that takes place at your first intervertebral joint.
The first intervertebral joint is the topmost spinal joint; it is the place where your head sits on your neck. This extension movement brings the head backward. A contraction of both SCM muscles also flexes your neck, which brings your chin down in the direction of your breastbone.
And bilateral SCM muscles contraction thrusts the chin forward when your head is level. Bilateral SCM muscle contraction simultaneously also plays a role in the breathing process.
In this case, it lifts up of the manubrium, which is another name for the breastbone. It also lifts the area of the collarbones that are nearest to the midline of the body.
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