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The muscles of the head and neck are a complex network of structures that work together to enable a wide range of movements. These include rotating, flexing, extending, and laterally bending the head. The neck muscles are responsible for supporting the weight of the skull and enabling movement, while also protecting vital neurovascular structures. They assist in functions such as chewing, swallowing, breathing, and making facial expressions. The head is moved by the contraction of muscles such as the sternocleidomastoid, splenius capitis, and trapezius, which originate from the neck and attach to the skull. These muscles, along with others like the suboccipital muscles, play a crucial role in maintaining head stability and facilitating various head movements.
| Characteristics | Values |
|---|---|
| Number of muscles in the neck | 30 |
| Functions | Support and move the head, chewing, swallowing, breathing, making facial expressions |
| Types | Skeletal, voluntary, lateral, posterior, suboccipital, transversospinalis, superficial, splenius capitis, splenius cervicis, cervical vertebrae, scapular, back, infrahyoid, suprahyoid, sternocleidomastoid, digastric, stylohyoid, mylohyoid, geniohyoid, omohyoid, thyrohyoid, sternothyroid, buccinator, orbicularis oris, orbicularis oculi, occipitofrontalis, masseters, temporalis, medial pterygoid, lateral pterygoid, tongue, extra-ocular, levator palpebrae superioris |
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What You'll Learn
The neck muscles that move the head
The neck is a complex structure of bones, muscles, nerves, blood vessels, lymphatics, and connective tissues. The neck muscles are skeletal muscles, meaning they are attached to bones by tendons. These muscles are under our voluntary control, allowing us to move our heads in various directions.
The splenius muscles, including the splenius capitis and splenius cervicis, are also involved in head movement. The splenius capitis, a posterior neck muscle, originates from the nuchal ligament and the C7 to T3 spinous processes, inserting onto the occipital and temporal bones. Bilateral contraction of the splenius capitis aids in head extension, while unilateral contraction assists in lateral flexion and rotation to the same side. The splenius cervicis extends into the cervical region and helps control head, shoulder, and vertebral column movements.
The suboccipital muscles, located just below the occipital bone, play a crucial role in fine motor control. They aid in making minor adjustments to head position and contribute to proprioception, our sense of self-movement and body position. The trapezius, another superficial muscle, assists in extending and tilting the head backward, in addition to controlling shoulder blade movements.
The scalene muscles are lateral neck muscles that help move the head and stabilise the cervical spine. They enable movements like twisting the head from side to side and tilting the cervical spine. The suprahyoid and infrahyoid muscles are also significant head flexors, working alongside the SCM.
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The splenius muscles
The splenius capitis is a deep muscle of the back 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 of the skull. 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. It acts as an extensor and lateral flexor of the neck, assisting with its rotation.
The splenius cervicis is also a deep, intrinsic muscle, but of the cervical and thoracic spine. Its fibres also run superiorly and laterally. It assists in ipsilateral cervical side flexion and rotation. When both splenius cervicis muscles contract, they extend the cervical spine.
Together, the splenius muscles extend and ipsilaterally rotate the head and neck. They also assist in supporting the head in an erect position. The splenius muscles are just one group of muscles that help to move the head. 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. The cervical spine, in particular, is designed to support the skull while still allowing for movement.
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The suboccipital muscles
The rectus capitis posterior major is the larger of the two rectus capitis muscles and originates from the spinous process of the C2 vertebra (axis). It inserts into the lateral part of the inferior nuchal line of the occipital bone. This muscle is involved in extension and rotation of the head to the ipsilateral side.
The rectus capitis posterior minor is the most medial of the suboccipital muscles and has a connective tissue bridge to the dura mater, which may contribute to cervicogenic headaches. It originates from the posterior tubercle of the C1 vertebra (atlas) and attaches to the medial part of the inferior nuchal line of the occipital bone. This muscle is also responsible for extension and rotation of the head to the ipsilateral side.
The obliquus capitis superior is located laterally in the suboccipital compartment and is smaller than the obliquus capitis inferior. It originates from the transverse process of the C1 vertebra (atlas) and attaches to the occipital bone between the superior and inferior nuchal lines. This muscle contributes to extension of the head.
The obliquus capitis inferior is the most inferiorly positioned of the suboccipital muscles and is the only one that does not attach to the cranium. It inserts into the transverse process of the atlas on the inferoposterior part and originates from the posterior tubercle of the posterior arch of the axis. This muscle aids in rotating the head to the ipsilateral side.
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The oral muscles of facial expression
The muscles of facial expression are located within the subcutaneous tissue of the face, originating from bone or fascia and inserting into the skin. They pull on the skin as they contract, producing movements of the face such as smiling, grinning, frowning, and raising eyebrows. These muscles are commonly called mimetic muscles. The facial muscles can be broadly categorized into three groups: orbital, nasal, and oral.
The orbicularis oris is a circular muscle that closes the lips to narrow the oral opening. It arises from the maxilla and other muscles of the cheek, inserting into the skin and mucous membrane of the lips. The buccinator is a thin, square-shaped muscle located deep to the other muscles of the face, between the mandible and maxilla. It functions to compress the cheek against the molar teeth, preventing them from being bitten during mastication. Additionally, the buccinator helps keep the bolus of food central in the oral cavity, preventing it from escaping into the oral vestibule. It also plays a role in whistling and playing wind instruments by allowing air to be blown from the inflated vestibule through cheek compression.
The buccolabial group of muscles, which includes the buccinator and other muscles like the depressor anguli oris, depressor labii inferioris, levator anguli oris, levator labii superioris, and mentalis, forms a functional compound that controls the shape and movements of the mouth and lips. These muscles enable a range of expressions, from smiling to frowning and showing disgust.
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The muscles of mastication
The temporalis muscle is a large, flat, fan-shaped muscle that lies within the temporal fossa of the skull. It arises from the entirety of the temporal fossa below the temporal line and its fibres converge anteriorly to form a tendon that inserts on the apex and medial surface of the coronoid process. The masseter muscle is a strong, quadrangular muscle that covers the lateral aspect of the ramus of the mandible. It is composed of two layers that differ slightly in their attachments. The medial pterygoid muscle is also quadrangular and is situated in the infratemporal fossa. It is composed of two heads that have two sets of origins, with the larger deep head arising from the medial surface of the lateral pterygoid plate of the sphenoid bone. The lateral pterygoid muscle fibres converge inferiorly, forming a tendon that inserts on the pterygoid fovea of the neck of the condylar process of the mandible.
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Frequently asked questions
The neck muscles are the main muscles that move the head. There are about 30 muscles in the neck that allow for a wide range of movements, including rotation, flexion, extension, and lateral bending.
Examples of neck muscles include the splenius capitis, splenius cervicis, trapezius, and sternocleidomastoid.
The splenius capitis muscle aids in head extension, lateral flexion, and rotation to the same side.
The sternocleidomastoid muscle helps bend the head forward when contracted bilaterally. When contracted unilaterally, it facilitates lateral flexion on the same side or head rotation to the opposite side.
The superficial neck muscles help with head extension and rotation, while the deep neck muscles, including the suboccipital muscles, aid in fine motor control and minor adjustments of head position.
