Victor Forge
The human body is a complex network of muscles, each with its own unique function. One such function is the extension of the head, which is facilitated by several muscles. The trapezius muscle, for instance, is a large, triangular muscle located in the upper back and neck region, and it plays a crucial role in both shoulder movement and head extension. The splenius muscles are also responsible for extending the head when contracted bilaterally. Additionally, the cervical transversospinalis muscles, including the semispinalis capitis and cervicis, contribute to head extension during bilateral contraction. Furthermore, the rectus capitis posterior minor and major muscles act at the atlanto-occipital joint, enabling the extension and rotation of the head. Understanding these muscles and their functions provides insight into the intricate mechanics of the human body and its diverse range of movements.
| Characteristics | Values |
|---|---|
| Muscle that extends the head | Trapezius |
| Location | Upper back and neck |
| Shape | Triangular |
| Function | Shoulder movement, specifically shoulder elevation, and head extension |
| Other functions | Other movements and postures of the upper body |
| Head extension | Backward movement of the head, as if looking up towards the ceiling |
| Other muscles that extend the head | Splenius muscles, Semispinalis capitis, Rectus capitis posterior minor, Rectus capitis posterior major |
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What You'll Learn
The trapezius muscle
The trapezius is made up of particularly long muscle fibres that span a large width of the upper back. This enables the trapezius to assist in mainly postural attributes, allowing and supporting the spinal column to remain erect when the person is standing. The muscle works in conjunction with several muscles to produce coordinated movements, primarily involving the scapula.
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The splenius muscles
The splenius capitis is a deep muscle of the neck. It originates from the lower half of the nuchal ligament and the spinous processes of the seventh cervical vertebra and the superior three thoracic vertebrae. The muscle fibres run superiorly and laterally, inserting into the mastoid process of the temporal bone. The mastoid process is a pyramidal-shaped eminence on the base of the skull. The splenius capitis also inserts in part onto the external surface of the occipital bone, below the lateral section of the superior nuchal line.
The splenius capitis acts as an extensor and lateral flexor of the neck, and assists with its rotation. It also forms part of the floor of the posterior triangle of the neck. This triangle is formed by the posterior border of the sternocleidomastoid, the anterior border of the trapezius, and the superior margin of the clavicle as the base. Bilateral contraction of the splenius capitis results in the extension of the head on the neck. When it contracts unilaterally, it acts in synergy with the contralateral sternocleidomastoid muscle, resulting in lateral flexion and rotation of the head towards the ipsilateral side.
The splenius cervicis is also a deep, intrinsic muscle, but of the cervical and thoracic spine. Its fibres run superiorly and laterally. It assists in ipsilateral cervical side flexion and rotation. When both splenius cervicis muscles contract, they extend the cervical spine. Bilaterally, they extend the neck, and unilaterally, they laterally flex and rotate the head and neck to the ipsilateral side. The splenius cervicis also assists in supporting the head in the erect position.
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The cervical transversospinalis muscles
The semispinalis muscles are the most superficial of the transversospinalis muscle group and have the longest fascicles, spanning six segments. They originate from the transverse processes of the vertebrae and cross between four and six vertebrae to attach to the spinous processes. The semispinalis muscles include the semispinalis capitis, semispinalis cervicis, and semispinalis thoracis. The semispinalis capitis is the highest muscle in this group and helps to bend the head. It arises from the articular processes of vertebrae C4-C7 and the transverse processes of vertebrae T1-T6, inserting onto the occipital bone at the base of the skull. The semispinalis cervicis arises from the transverse processes of vertebrae T1-T6 and inserts onto the spinous processes of vertebrae C2-C5.
The multifidus muscle lies deep to the semispinalis and spans the entire length of the vertebral column, providing essential support and stability for the spine. It is most developed in the lumbar region. The multifidus muscle originates from the transverse process and crosses between two and four vertebrae to attach to the spinous process.
The rotatores muscles are the deepest muscles in the transversospinalis group and have the shortest fascicles, spanning one to two segments. They lie beneath the multifidus and run up and down the entire spine, although they are most present in the thoracic region. The rotatores muscles include the rotatores capitis, rotatores cervicis, and rotatores thoracis. The rotatores thoracis is the most developed in this group. The cervical-level and lumbar-level rotatores may be represented by deeper fascicles of the multifidus.
Overall, the cervical transversospinalis muscles play an important role in spinal stability, proprioception, and posture, helping to stabilize the vertebral column and maintain proper posture.
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The sternocleidomastoid muscles
The sternocleidomastoid (SCM) muscle is a powerful neck muscle that allows you to bend your neck and turn or tilt your head. It is the largest muscle in the front of your neck and is located just below your skin on both the right and left sides of your neck. The SCM muscle extends from the mastoid process at the base of your skull to your collarbones (clavicles) and breastbone (sternum). The SCM muscle ends at the mastoid process, which is short for a section of bone called the mastoid process, located at the base of your skull behind your ears.
The sternocleidomastoid muscle is closely related to certain neurovascular structures that pass through the neck on their way to the head or to the periphery of the body. The sternal head originates from the manubrium of the sternum, while the clavicular head originates from the medial third of the clavicle. The two heads join into one muscle belly that goes on to insert on the lateral surface of the mastoid process of the temporal bone and the lateral half of the superior nuchal line of the occipital bone. The SCM muscle is innervated by the accessory nerve (cranial nerve XI) and direct branches of the cervical plexus (C2-C3).
A unilateral contraction of the SCM muscle flexes the cervical vertebral column to the same side (lateral flexion) and rotates the head to the opposite side. A bilateral contraction elevates the head by dorsally extending the upper cervical joints. When the head and neck are fixed, the SCM can also elevate the sternum and clavicle, expanding the thoracic cavity during forced inspiration.
Injuries, tension, sprains, strains, atrophy, and tumours can all damage the SCM muscle. SCM syndrome, an acute or chronic condition involving neck stiffness, pain, and other symptoms, can occur when part of the SCM muscle develops tightened, sensitive areas, or trigger points. Treatments for SCM issues include massage, osteopathic manipulation, physical therapy, and surgery in severe cases. It is also important to manage stress and maintain good posture to care for the SCM muscle.
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The rectus capitis posterior minor muscle
The function of the rectus capitis posterior minor muscle is to support and enable head and neck movements. It helps to extend the head and neck during bilateral contraction and laterally flex and rotate the head to the opposite side during unilateral contraction. This muscle plays an important postural role, stabilizing the head during various body movements.
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Frequently asked questions
The trapezius muscle is involved in both shoulder movement and head extension. The lower fibres of the trapezius muscle are responsible for extending the head.
The trapezius is a large, triangular muscle located on the upper back and neck. It is a muscle that people often enjoy having massaged.
The splenius muscles extend the head when contracted bilaterally. The rectus capitis posterior major and minor muscles also extend the head and neck.
