Dominic Stone
The head and neck are supported by a complex musculoskeletal system that allows for a wide range of movements. There are about 30 neck muscles that help stabilize the head, neck, and upper spine, and enable us to perform essential functions such as chewing, swallowing, and breathing. These muscles also assist in maintaining balance and protecting vital neurovascular structures. The neck muscles can be categorized into three groups: anterior (front), lateral (side), and posterior (back). The SCM (sternocleidomastoid) muscle, for example, is a powerful anterior neck muscle that allows us to bend, turn, and tilt our heads. The SCM works in conjunction with other neck muscles to support the temporomandibular joint (TMJ), which enables us to open and close our mouths for chewing and speaking.
| Characteristics | Values |
|---|---|
| Number of neck muscles | 30 |
| Neck muscle categories | anterior (front), lateral (side), posterior (back) |
| Anterior neck muscles | superficial, suprahyoid, infrahyoid, scalene muscles |
| Largest anterior neck muscle | Sternocleidomastoid (SCM) |
| Superficial muscle function | Controls shoulder blade movements, assists in extending and tilting the head backward |
| Transversospinalis muscles function | Move the head forward and backward, tilt it from side to side, stabilize the spine |
| Muscle involved in closing the eye | Orbicularis oculi |
| Muscle that moves the eyebrows and scalp | Occipitofrontalis |
| Muscle that moves the lips | Orbicularis oris |
| Main muscle used for chewing | Masseter |
| Muscle that moves the tongue downward and forward | Genioglossus |
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What You'll Learn
Neck muscles that support the head
The neck is a complex structure of bones, muscles, nerves, blood vessels, and connective tissues. There are about 30 neck muscles that support the head and allow for a wide range of movements. These muscles also assist with chewing, swallowing, and breathing.
Neck muscles can be categorized into three main groups: anterior (front), lateral (side), and posterior (back). The anterior neck muscles can be further divided into four regions: superficial, suprahyoid, infrahyoid, and scalene muscles. The suprahyoid muscles control the movement of the hyoid bone (located just below the jawline) during swallowing and speaking. The infrahyoid muscles, on the other hand, move the larynx up and down. The scalene muscles aid in breathing by moving the first two ribs and help stabilize the cervical spine.
The lateral neck muscles enable head movements from the base of the skull and allow for twisting and tilting of the head and cervical spine. The posterior neck muscles include the superficial, suboccipital, and transversospinalis muscles. The superficial muscles are strap-like muscles that help extend and rotate the head. The transversospinalis muscles assist in moving the head forward and backward and tilting it side to side. They also contribute to spine stabilization.
In addition to these muscle groups, the cervical spine, or the bony part of the neck, plays a crucial role in supporting the skull while permitting flexibility for various movements. The OA joint, formed by the connection between the occipital condyles and the C1 vertebra, provides attachment points for some neck muscles and helps bear the weight of the skull.
Overall, the neck muscles and associated structures work together to support the head, facilitate movements, and enable essential functions such as chewing, swallowing, and breathing.
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Muscles involved in chewing
Chewing, or mastication, involves several muscles working together to break down food into digestible pieces. The main muscles involved in this process are the masseter, temporalis, medial pterygoid, and lateral pterygoid.
The masseter muscle is the most powerful muscle involved in chewing. It is responsible for elevating the mandible (lower jaw) to close the mouth. The masseter has two parts: deep and superficial. The deep fibres of the masseter help to retract the mandible, while the superficial fibres protrude it. The masseter muscle is innervated by the mandibular nerve (V3) and receives its blood supply from the masseteric artery, a branch of the maxillary artery.
The temporalis muscle assists the masseter in elevating and closing the jaw. It originates from the temporal fossa of the skull and attaches to the coronoid process of the mandible. The temporalis muscle is also innervated by the mandibular nerve (V3) and receives its blood supply from the deep temporal part of the maxillary artery and its superficial branches.
The medial pterygoid and lateral pterygoid muscles also play a crucial role in chewing. The medial pterygoid assists in chewing and moving food within the mouth. It has two heads: deep and superficial. The lateral pterygoid is involved in opening the mouth and protrusive movements. It has two heads, superior and inferior, which converge into a tendon attaching to the neck of the mandible. Both the medial and lateral pterygoid muscles are innervated by the mandibular nerve (V3).
In addition to these primary muscles, the buccinator muscle in the cheek also contributes to the action of chewing. It compresses the cheek, enabling us to whistle, blow, and suck. The suprahyoid muscles in the neck also play a supporting role during chewing, as they help with swallowing.
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Muscles that control tongue movement
The tongue is a muscular organ formed by a complex arrangement of intrinsic and extrinsic muscles. Tongue muscles can be extrinsic or intrinsic. Extrinsic tongue muscles insert into the tongue from outside origins, and the intrinsic tongue muscles insert into the tongue from origins within it. The extrinsic muscles move the whole tongue in different directions, whereas the intrinsic muscles allow the tongue to change its shape (such as curling the tongue or flattening it).
The genioglossus muscle is a large, thick muscle that contributes significantly to the shape of the tongue. It arises from the mandibular symphysis, inserting onto the body of the hyoid bone and the entire length of the tongue. It is responsible for protrusion (sticking the tongue out) and depression of the tongue. The genioglossus muscle is innervated by the hypoglossal nerve.
The hyoglossus muscle is located in the floor of the oral cavity, immediately lateral to the geniohyoid. It arises from the hyoid bone and inserts onto the lateral aspect of the tongue. The hyoglossus muscle is responsible for depression and retraction of the tongue. Like the genioglossus muscle, it is innervated by the hypoglossal nerve.
The styloglossus is a thin, paired muscle, located on either side of the oropharynx. It originates from the styloid process of the temporal bone and inserts onto the lateral aspect of the tongue. The styloglossus is responsible for retraction and elevation of the tongue. It is innervated by the hypoglossal nerve.
The palatoglossus muscle is associated with the soft palate and is innervated by the vagus nerve. It arises from the palatine aponeurosis and inserts broadly along the tongue. Contraction of the palatoglossus muscle elevates the posterior tongue, closes the oropharyngeal isthmus, aids in the initiation of swallowing, and prevents the spill of saliva from the vestibule into the oropharynx by maintaining the palatoglossal arch.
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Muscles that control eye movement
The human eye has six muscles that control its movement, known as "external" or "extrinsic" muscles. These muscles work in pairs, with one muscle moving and its partner controlling and balancing that movement. This is why human eyes can only turn so far. These muscles are also referred to as extraocular muscles and can be divided into two groups: the four recti muscles and the two oblique muscles.
The four recti muscles are the superior rectus, inferior rectus, medial rectus, and lateral rectus. They originate from the common tendinous ring, a ring of fibrous tissue that surrounds the optic canal at the back of the orbit. From their origin, the muscles pass anteriorly to attach to the sclera of the eyeball. The name "recti" is derived from the Latin word for "straight", representing the direct path these muscles take from origin to attachment.
The two oblique muscles are the superior oblique and inferior oblique. Unlike the recti group, the oblique muscles do not originate from the common tendinous ring. Instead, they take an angular approach to the eyeball.
These six muscles are responsible for eye movements along three different axes: horizontal, vertical, and torsional. Horizontal movements are controlled entirely by the medial and lateral rectus muscles, with the medial rectus responsible for adduction (movement towards the nose) and the lateral rectus responsible for abduction (movement away from the nose). Vertical movements require the coordinated action of the superior and inferior rectus muscles, as well as the oblique muscles. The relative contribution of the rectus and oblique groups depends on the horizontal position of the eye. In the primary position (eyes straight ahead), both groups contribute to vertical movements. Elevation is achieved through the action of the superior rectus and inferior oblique muscles, while depression results from the action of the inferior rectus and superior oblique muscles. When the eye is abducted, the rectus muscles are the prime vertical movers, with elevation caused by the superior rectus and depression by the inferior rectus. When the eye is adducted, the oblique muscles take the lead, with elevation due to the inferior oblique muscle and depression due to the superior oblique muscle. The oblique muscles are also primarily responsible for torsional movements.
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Sternocleidomastoid (SCM) muscle
The sternocleidomastoid (SCM) muscle is a two-headed neck muscle that attaches to the manubrium of the sternum (sterno-), the clavicle (-cleido-), and the mastoid process of the temporal bone (-mastoid). It is the largest muscle in the front of the neck and is easily visible and palpable. The SCM muscle helps to stabilise the neck and allows for a range of movements, including bending, turning, and tilting the head.
The SCM muscle originates from the manubrium of the sternum and the medial third of the clavicle. These two heads join to form a single muscle belly, which inserts on the lateral surface of the mastoid process and the lateral half of the superior nuchal line of the occipital bone. The SCM muscle is unique in that it has variable innervations, with the "classical anastomotic pattern" observed in approximately half of cases.
The SCM muscle plays a crucial role in various functions. Firstly, it assists in breathing by lifting the breastbone and collarbone during inhalation. Additionally, it supports the temporomandibular joint (TMJ), enabling the mouth to open and close during chewing. The SCM muscle also helps maintain posture and stabilises the neck, even when the body is at rest.
Injuries, tension, and conditions like sternocleidomastoid syndrome can cause pain and stiffness in the SCM muscle. Treatment options include conservative approaches such as stretching, physical therapy, hot and cold therapy, massage, and osteopathic manipulation. In severe cases, surgery may be necessary if conservative treatments are ineffective or if there is significant structural damage, such as a major tear or a tumour.
The SCM muscle is an important landmark in the neck, dividing it into anterior and posterior triangles. It also protects vital neurovascular structures in the neck, including branches of the cervical plexus and deep cervical lymph nodes. Overall, the SCM muscle is a vital component of the musculoskeletal system, enabling various movements and supporting essential functions.
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Frequently asked questions
The masseter muscle is the main muscle used for chewing, as it elevates the mandible (lower jaw) to close the mouth. It is assisted by the temporalis muscle, which retracts the mandible.
The orbicularis oculi is a circular muscle that closes the eye. The occipitofrontalis muscle moves up the scalp and eyebrows.
The bilateral sternocleidomastoid (SCM) is a major head flexor, along with the suprahyoid and infrahyoid muscles. The SCM allows you to bend your neck and turn or tilt your head.
Tongue muscles can be extrinsic or intrinsic. Extrinsic muscles move the whole tongue in different directions, while intrinsic muscles allow the tongue to change its shape.
There are about 30 muscles in the neck that help stabilise and support the head and upper back. They also assist with chewing, swallowing, and breathing.
