Dominic Stone
The neck is a complex structure of bones, muscles, nerves, blood vessels, and connective tissues that connects the head to the torso. There are about 30 neck muscles that support and stabilise the head, neck, and upper spine, enabling a wide range of head movements, including rotation, flexion, extension, and lateral bending. These muscles also assist with vital functions such as chewing, swallowing, and breathing. The sternocleidomastoid (SCM) muscle, for example, is a major head flexor that helps bend the head forward when contracted bilaterally, while unilateral contraction facilitates lateral flexion and head rotation. The rectus capitis lateralis flexes the head laterally, and the longus capitis acts as a weak head flexor when contracted bilaterally. The splenius capitis and semispinalis capitis muscles help extend and rotate the head, allowing us to look up and turn our heads from side to side.
| Characteristics | Values |
|---|---|
| Number of neck muscles | 30 |
| Function | Support and stabilise the head, neck and upper spine; enable head movement; assist with chewing, swallowing and breathing |
| Types | Anterior, lateral (prevertebral), and posterior |
| Examples of anterior muscles | Rectus capitis anterior, rectus capitis lateralis, longus capitis, longus colli |
| Examples of lateral muscles | Anterior, middle, and posterior scalenes |
| Examples of posterior muscles | Superficial, suboccipital, transversospinalis, trapezius, splenius capitis, splenius cervicis |
| Examples of flexor muscles | Bilateral sternocleidomastoid (SCM), suprahyoid, infrahyoid, longus capitis |
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What You'll Learn
- The SCM, suprahyoid, and infrahyoid muscles help to bend the head forward
- The splenius capitis and cervicis extend the head and neck
- The rectus capitis lateralis flexes the head laterally
- The longus capitis acts as a weak flexor of the head
- The scalene muscles help move the head and stabilise the cervical spine
The SCM, suprahyoid, and infrahyoid muscles help to bend the head forward
The muscles in the neck support the head and enable a wide range of head movements, including rotation, flexion, extension, and lateral bending. The SCM (sternocleidomastoid), suprahyoid, and infrahyoid muscles are significant flexors that help bend the head forward.
The SCM is a large and easily recognisable muscle that originates at the sternum and clavicle and attaches to the mastoid process of the temporal bone. When the SCM contracts bilaterally, it helps to bend the head forward. On the other hand, unilateral contraction causes lateral flexion to the same side or head rotation to the opposite side.
The suprahyoid and infrahyoid muscles are hyoid muscles that attach to the hyoid bone. There are eight hyoid muscles in total, with four suprahyoid and four infrahyoid muscles. The suprahyoid muscles lie above the hyoid bone, while the infrahyoid muscles lie beneath it. These muscles work together to stabilise the trachea and play a crucial role in swallowing and speech.
When the infrahyoid muscles contract, they depress the hyoid bone, allowing the suprahyoid muscles to contract and depress the mandible. Conversely, if the suprahyoid muscles contract while the infrahyoid muscles are relaxed, the hyoid bone is elevated. The suprahyoid muscles also contribute to the floor of the mouth and include the digastric, stylohyoid, mylohyoid, and geniohyoid muscles.
In summary, the SCM, suprahyoid, and infrahyoid muscles are essential for bending the head forward and facilitating other head movements. They work in coordination with other neck muscles to enable the wide range of motions that the head and neck are capable of.
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The splenius capitis and cervicis extend the head and neck
The neck is a complex structure of bones, muscles, nerves, blood vessels, lymphatics, and connective tissues. It connects the head to the torso and supports the skull, allowing for a wide range of movements. The neck muscles play a crucial role in various functions, including chewing, swallowing, breathing, and moving the head.
The splenius capitis and splenius cervicis are deep muscles located in the back of the neck. They are responsible for extending the head and neck, as well as lateral flexion and rotation. The splenius capitis originates from the lower half of the nuchal ligament and the spinous processes of the seventh cervical vertebra (C7) and the first three thoracic vertebrae (T1-T3). It inserts onto the mastoid process of the temporal bone and acts as an extensor and lateral flexor of the neck.
The splenius cervicis is also a deep muscle of the cervical and thoracic spine. Its fibres run superiorly and laterally. When both splenius cervicis muscles contract, they extend the cervical spine and neck. Unilaterally, they laterally flex and rotate the head and neck to the same side.
The coordination of the splenius capitis and splenius cervicis muscles allows for smooth and controlled movements of the head and neck. Their extension, flexion, and rotation capabilities enable us to perform various daily activities and maintain our balance. These muscles work in synergy with other neck muscles, such as the sternocleidomastoid, to facilitate a wide range of motions.
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The rectus capitis lateralis flexes the head laterally
The human neck is a complex structure of bones, muscles, nerves, blood vessels, and connective tissues. It is made up of around 30 muscles that support and stabilise the head, neck, and upper spine, while also facilitating a range of movements. These muscles are skeletal muscles, meaning they are attached to bones by tendons. They are voluntary muscles, so we are able to control how they move and work.
The rectus capitis lateralis is one of the many muscles in the neck. It is a suboccipital muscle, located in the upper back part of the neck. The rectus capitis lateralis muscle is involved in extending the head on the neck and rotating it to the side. When both muscles contract bilaterally, they extend the head on the neck, while unilateral contraction rotates the head to the ipsilateral side at the atlanto-axial joint.
The rectus capitis lateralis muscle is triangular in shape. Its fibres pass superolaterally, attaching to the spinous process of the axis (the second cervical vertebra) and inserting on the lateral part of the inferior nuchal line and the occipital bone. This muscle is innervated by the suboccipital nerve, specifically the posterior ramus of cervical spinal nerve C1.
The function of the neck muscles is to support the head and enable various movements, including chewing, swallowing, and breathing. The neck also acts as a conduit for the brain to communicate with the body, allowing for the transmission of motor and sensory information and nutrients. The flexibility of the cervical spine, which is the bony part of the neck, allows for large movements to scan surroundings and adjust to the environment.
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The longus capitis acts as a weak flexor of the head
The longus capitis is a long, flat muscle of the anterior neck. It runs up the length of the cervical spine, adjacent to the vertebral bodies. It is the most superficial muscle of the prevertebral muscle group. The muscle originates from the inferior aspect of the cervical spine, with fibres running superomedially and converging into a single broad muscle belly. The muscle inserts onto the basilar part of the occipital bone, anterior to the insertion of the rectus capitis anterior muscle. The longus capitis is innervated by anterior rami of the spinal nerves C1-C3 and occasionally C4. It is supplied with blood by the muscular branches of the ascending cervical artery and the inferior thyroid artery.
The neck is a complex structure of bones, muscles, nerves, blood vessels, lymphatics, and other connective tissues. It is the most flexible part of the spine, allowing for large movements to scan our surroundings and adjust to our environment. The neck also has the vital role of acting as a conduit for the brain to communicate with the rest of the body.
The neck muscles support the head and enable a variety of movements, including chewing, swallowing, and breathing. They also assist in stabilising the bones in the neck (cervical spine). The lateral neck muscles control head movements from the base of the skull, allowing the head to twist and tilt. The suboccipital muscles, located just below the occipital bone at the base of the skull, help extend the head in different directions.
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The scalene muscles help move the head and stabilise the cervical spine
The human neck is a complex structure of bones, muscles, nerves, blood vessels, lymphatics, and other connective tissues. The neck muscles support the head and enable a wide range of movements, including turning the head from side to side, bending it forward or backward, and tilting it. They also assist with essential functions such as chewing, swallowing, and breathing.
The scalene muscles are a group of deep muscles located laterally in the neck, enclosed by the deep fascia, also known as the prevertebral fascia. These muscles include the anterior scalene, middle scalene, posterior scalene, and scalenus minimus, which is present in approximately 30% to 71% of individuals. The scalene muscles play a crucial role in moving the head and stabilising the cervical spine, which is the bony part of the neck that supports the skull while allowing for a wide range of movements.
The anterior scalene, in particular, is involved in neck flexion, which occurs when you bring your chin down towards your chest. It also contributes to the initial degrees of head rotation, such as when you turn your head to look over your shoulder. The scalene muscles work in conjunction with other neck muscles, such as the sternocleidomastoid and the splenius capitis, to facilitate these movements.
In addition to their role in neck and head movement, the scalene muscles are also important for respiration. They help elevate the first and second ribs during inhalation, acting as secondary respiratory muscles. This function is facilitated by the electrical activity that persists in the scalene muscles even during non-forced breathing. Their proximity to major vessels and nerves makes them clinically significant, especially in surgical procedures and the management of conditions in the cervicothoracic area.
Dysfunction or injury to the scalene muscles can lead to pathological conditions such as thoracic outlet syndrome (TOS), reduced ventilatory capacity, and cervical pain. Rehabilitation and medical interventions focus on restoring muscle function and reducing excessive muscle tone to alleviate these issues.
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Frequently asked questions
The muscles that flex the head are a complex group of structures that work together to allow a wide range of head movements. These include the bilateral sternocleidomastoid (SCM), and the suprahyoid and infrahyoid muscles. The SCM contracts bilaterally to bend the head forward, while unilateral contraction causes lateral flexion on the same side or head rotation to the opposite side.
Examples of head flexion movements include bending the head forward towards the chest (cervical flexion) and bending the head backward (cervical extension).
There are about 30 neck muscles that help with head movement and support. Some of these include the splenius capitis, splenius cervicis, and the scalene muscles.
