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The neck is a complex structure of bones, muscles, nerves, blood vessels, and connective tissues that support the skull and enable head movement. The neck muscles are skeletal muscles, attached to bones by tendons, and can be categorized into anterior, lateral, and posterior muscles. The lateral and posterior neck muscles, such as the splenius muscles, control head movements, allowing for rotation, flexion, and extension of the head. The specific muscles involved in rotating the head left include the sternocleidomastoid, splenius capitis, semispinalis capitis, and longus capitis muscles. These muscles contract to enable the rotational movement of the head to the left or right.
| Characteristics | Values |
|---|---|
| Number of neck muscles | 30 |
| Neck muscle groups | Anterior, lateral (prevertebral), and posterior |
| Lateral neck muscles | Control head movements from the base of the skull |
| Superficial posterior neck muscles | Strap-like muscles in the back of the neck that help extend and rotate the head |
| Suboccipital posterior neck muscles | Located just below the occipital bone at the base of the skull, these muscles help extend the head in different directions |
| Transversospinalis posterior neck muscles | Help move the head forward and backward, tilt it from side to side, stabilize the spine, and move the cervical, thoracic, and lumbar regions of the spine |
| Splenius muscles | Extend the head when contracted bilaterally; unilateral contraction produces lateral flexion and rotation of the head to the same side |
| Trapezius muscle | Produces lateral flexion and contralateral rotation of the head when acting unilaterally; extension of the head when acting bilaterally |
| Semispinalis capitis and cervicis muscles | Extension of the head, cervical, and thoracic spine by bilateral contraction; ipsilateral lateral flexion of the head, cervical, and thoracic spine by unilateral contraction; contralateral rotation of the head, cervical, and thoracic spine by unilateral contraction |
| Longus capitis muscle | Weak flexor of the head when acting bilaterally; unilateral contraction produces ipsilateral rotation of the head |
| Longus colli (or longus cervicis) muscle | A long muscle that spans the entire length of the cervical spine and the upper vertebrae of the thoracic spine |
| Sternocleidomastoid muscle | Ipsilateral flexion and contralateral rotation of the neck at the cervical spine |
| Rotatores cervicis muscles | Extension of the spine by bilateral contraction, lateral flexion of the spine by unilateral contraction |
| Interspinales muscles | Extension of the cervical and lumbar spine |
| Intertransversarii muscles | Assist in lateral flexion of the spine and stabilization of the spine |
| Cervical dystonia (or spasmodic torticollis) | A condition due to an abnormal sternocleidomastoid (SCM) muscle contracture that causes a rotational deformity away from the affected side with a head tilt toward the affected side |
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What You'll Learn
The role of the splenius muscles
The neck is a complex structure of bones, muscles, nerves, blood vessels, lymphatics, and other connective tissues. It is made up of around 30 muscles, which support and stabilise the head, neck, and upper spine, while also helping with chewing, swallowing, and breathing.
The splenius muscles are a group of superficial muscles in the back of the neck. They are the splenius capitis and splenius cervicis, which also belong to the superficial layer of the deep (intrinsic) back muscles. The splenius capitis is a thick, flat muscle arising from the spinous processes of the seventh cervical to the third thoracic vertebrae (C7-T3). The splenius cervicis arises from the upper thoracic and lower cervical spinous processes.
The function of the splenius muscles is to extend the head when contracted bilaterally. When contracted unilaterally, they produce lateral flexion and rotation of the head to the same side. The splenius capitis also assists in supporting the head in the erect position. It acts as an extensor and lateral flexor of the neck, and helps with its rotation. Dysfunction of the splenius capitis may be found in those with mechanical chronic neck pain or whiplash disorders.
The most common cause of muscle tension headache (MTH) results from inflammatory changes at the site of muscular attachment on the occipital ridge. This occurs most often at the attachment of the splenius capitis muscles, causing splenius capitis muscle syndrome. This is a very painful and common syndrome that typically mimics the respective pain reference patterns of temporal tendinitis and migraine headaches.
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The longus capitis
The neck is a complex structure of bones, muscles, nerves, blood vessels, lymphatics, and connective tissues that connect the head to the torso. The cervical spine, composed of seven vertebrae, allows for flexion, extension, rotation, and side-bending. The neck muscles support and stabilise the head, enabling various movements, including chewing, swallowing, and breathing. They also assist in sensory and motor functions by facilitating the transmission of information and nutrients between the body and the head.
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The trapezius muscle
The main function of the trapezius is to produce lateral flexion and contralateral rotation of the head when acting unilaterally, and extension of the head when acting bilaterally. The trapezius muscle stabilises and produces movements of the scapula. Depending on which part of the trapezius contracts, these movements may be elevation, depression, retraction, and rotation of the scapula. The trapezius muscle works in conjunction with several muscles to produce coordinated movements, primarily involving the scapula. Some key muscle pairings include the rhomboids, serratus anterior, levator scapulae, deltoid, and latissimus dorsi.
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The lateral neck muscles
The neck muscles are a complex musculoskeletal system that connects the base of the skull to the torso. There are about 30 neck muscles, which can be categorised into three main groups: anterior, lateral, and posterior. The lateral neck muscles, also known as the lateral vertebral muscles, control head movements from the base of the skull. They help with twisting and tilting the head from side to side and twisting and tilting the cervical spine.
The sternocleidomastoid muscle is a large, two-headed neck muscle that produces lateral flexion and rotation of the head. It originates from the medial third of the clavicle and the manubrium of the sternum, ascending diagonally to insert onto the mastoid process of the temporal bone. The function of this muscle depends on whether it acts alone or with its counterpart. Unilateral contraction results in lateral flexion of the neck on the same side and lateral rotation of the head to the opposite side. In contrast, bilateral contraction produces flexion of the neck, drawing the head towards the chest.
The longus colli, also known as the longus cervicis, is a long muscle spanning the cervical spine's entire length and the upper vertebrae of the thoracic spine. It is divided into three parts, with the superior part arising from the anterior tubercles of transverse processes of vertebrae C3-C5 and inserting into the anterior tubercle of vertebra C1. The inferior part of the longus colli can produce weak ipsilateral flexion and contralateral rotation of the neck.
The trapezius muscle is responsible for producing lateral flexion and contralateral rotation of the head when acting unilaterally and extending the head when acting bilaterally. It stabilises and moves the scapula, with specific contractions resulting in elevation, depression, retraction, and rotation of the scapula.
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Sternocleidomastoid muscle
The sternocleidomastoid (SCM) muscle is a powerful neck muscle that allows you to bend, turn, and tilt your head. It is the largest muscle in the front of your neck and can be felt on both the right and left sides. SCM syndrome, an acute or chronic condition involving neck stiffness and pain, can occur when part of the SCM muscle develops tightened, sensitive areas, or trigger points.
The SCM muscle originates from the base of the skull (mastoid process) and extends down both sides of the neck to the sternum (sternal head) and collarbone (clavicle). The SCM muscle has two heads that are separated at their origins by a triangular interval (lesser supraclavicular fossa) but blend together below the middle of the neck into a thick, rounded muscle. This muscle is innervated by the accessory nerve (CN XI) and anterior rami of spinal nerves C2 and C3. The vascular supply to the SCM muscle comes from branches of the occipital, posterior auricular, superior thyroid, and suprascapular arteries.
The function of the SCM muscle depends on whether it acts alone or together with its counterpart on the other side. When acting alone, unilateral contraction of the SCM muscle produces lateral flexion of the neck on the same side (ipsilateral) and lateral rotation of the head to the opposite side (contralateral). When acting together, bilateral contraction of the SCM muscles produces flexion of the neck, drawing the head towards the chest.
The SCM muscle also has other important functions. It helps to stabilize the neck and maintain posture. It works with other neck muscles to lift the breastbone and collarbone during inhalation, creating space for the lungs to take in air. Additionally, it supports the temporomandibular joint (TMJ), which allows for the opening and closing of the mouth.
Maintaining good posture, managing stress, and regular exercise can help care for the SCM muscle and prevent tension and injuries. Treatments for SCM muscle issues include massage, osteopathic manipulation, physical therapy, and in severe cases, surgery.
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Frequently asked questions
There are about 30 neck muscles that support and stabilise the head, neck, and upper spine, and allow for a range of movements. The muscles that rotate the head to the left include the sternocleidomastoid, splenius, and semispinalis muscles.
The sternocleidomastoid muscle is a key landmark in the neck as it divides the neck into anterior and vertebral regions. Unilateral contraction of this muscle produces lateral flexion of the neck and rotation of the head to the left.
The splenius muscles originate at the midline and run laterally and superiorly to their insertions. They can extend, laterally flex, and rotate the head.
The semispinalis muscles are part of the transversospinalis muscle group. They extend, laterally flex, and rotate the head, neck, and thoracic spine.
The neck muscles support the head and enable a variety of movements, including rotating the head from side to side. They also assist with chewing, swallowing, and breathing.
