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The muscles of the head and neck are responsible for a wide range of functions, including movement of the head and neck, chewing, swallowing, speech, facial expressions, and eye movements. The neck muscles, including the sternocleidomastoid and trapezius, provide gross motor movement to the head and neck, allowing for flexion, extension, and rotation. The head muscles include the tongue, muscles of facial expression, extra-ocular muscles, and muscles of mastication. These muscles enable essential functions such as chewing, speaking, and producing facial expressions. The facial muscles, in particular, are unique in that they primarily connect bones to skin, allowing for a wide range of expressions and movements.
| Characteristics | Values |
|---|---|
| Muscles responsible for head movement | Sternocleidomastoid, Trapezius, Splenius muscles, Occipitofrontalis, Transversospinalis, Scalene, Infrahyoid, Levator palpebrae superioris, Lateral rectus, Superior oblique, Lateral neck muscles, Posterior neck muscles, Suboccipital muscles, Epicranius |
| Muscles responsible for jaw movement | Masseters, Temporalis, Medial pterygoid, Lateral pterygoid |
| Muscles responsible for eye movement | Extra-ocular muscles, Superior rectus, Inferior rectus, Medial rectus, Lateral rectus, Superior oblique, Inferior oblique |
| Muscles responsible for lip movement | Orbicularis oris, Buccinator |
| Muscles responsible for facial expressions | Zygomaticus major, Zygomaticus minor, Buccinator |
| Smallest muscle in the head | Stapedius |
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What You'll Learn
Neck muscles that move the head
The neck muscles support the head and help with a range of movements, including chewing, swallowing, and breathing. There are about 30 muscles in the neck that enable a variety of movements. The neck muscles are innervated by various cervical nerves and their branches and cranial nerves.
The neck muscles that move the head include the sternocleidomastoid and the trapezius. These muscles are responsible for gross motor movement in the muscular system of the head and neck. They move the head in every direction, pulling the skull and jaw towards the shoulders, spine, and scapula. Working in pairs on the left and right sides of the body, these muscles control the flexion and extension of the head and neck. Working individually, these muscles rotate the head or flex the neck laterally to the left or right.
The splenius muscles, including the splenius capitis and splenius cervicis, are also involved in moving the head. These muscles originate at the midline and run laterally and superiorly, with the splenius capitis inserting into the head region and the splenius cervicis extending into the cervical region. They can extend, laterally flex, and rotate the head.
The transversospinalis muscles, including the semispinalis and multifidus muscles, help move the head forward and backward, as well as tilt it from side to side. They also assist in stabilising the spine and moving the cervical, thoracic, and lumbar regions of the spine.
Additionally, the scalene muscles are involved in head movement by helping to stabilise the bones in the neck (cervical spine) and enabling head rotation and cervical spine tilting.
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Muscles of mastication
The muscles of mastication are a group of muscles that enable chewing by moving the mandible (jaw) at the temporomandibular joint (TMJ). They also assist in grinding food and approximating the teeth. These muscles develop from the first pharyngeal arch and are innervated by the mandibular nerve (CNV3), a branch of the trigeminal nerve (CN V). The mandibular nerve is the only division of the trigeminal nerve that carries motor fibres.
The four muscles of mastication are the masseter, temporalis, medial pterygoid, and lateral pterygoid. The masseter muscle is the most powerful muscle of mastication. It has a rectangular shape with three layers (superficial, deep, and intermediate) and two parts (deep and superficial). Its main function is to elevate the mandible and approximate the teeth. The superficial head of the masseter is the only part that is visible.
The temporalis muscle is fan-shaped and originates from the temporal fossa of the skull, attaching to the coronoid process of the mandible. It assists in elevating and retracting the mandible. The medial pterygoid muscle has a quadrangular shape with two heads (deep and superficial) and is located inferiorly to the lateral pterygoid. The lateral pterygoid muscle has a triangular shape with two heads (superior and inferior) and is the major protractor of the mandible. It is the only muscle that causes depression of the mandible, along with assisting in protrusion and side-to-side movement.
The muscles of mastication work in coordination with the accessory muscles of mastication, which include the buccinator, suprahyoid, and infrahyoid muscles. The buccinator muscle helps in mastication by keeping food pushed back within the oral cavity. The suprahyoid muscle group consists of the digastric, mylohyoid, and geniohyoid muscles, which depress the mandible against resistance. The infrahyoid muscles include the sternohyoid, sternothyroid, thyrohyoid, and omohyoid, which fix or depress the hyoid bone.
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Muscles of facial expression
The muscles of facial expression are located within the subcutaneous tissue of the face. They originate from bone or fascia and insert into the skin. As these muscles contract, they pull on the skin to allow for facial expressions. These muscles develop from the second pharyngeal arch and are innervated by the facial nerve.
The muscles of facial expression can be divided into three groups based on their location: orbital, nasal, and oral. The orbital group contains two muscles associated with the eye socket, which are the only muscles that can close the eyelids. The nasal group contains the procerus, which is the most superior of the nasal muscles, and the depressor septi nasi. The oral group is responsible for movements of the mouth and lips and includes the orbicularis oris and the buccinator.
The facial muscles are unique in that they manipulate the skin and soft tissues, whereas other skeletal muscles move bones. They also have a higher fast-twitch fibre concentration and fewer mitochondria than other muscles. The orbicularis oculi and zygomaticus major are the fastest-moving muscles in the human body.
Facial muscles are essential for chewing, making facial expressions, and performing many other tasks. They are typically paired, with one muscle on each side of the face. The facial muscles involved in chewing include the lateral pterygoid, masseter, and temporalis.
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Extra-ocular muscles
The extraocular muscles, or extrinsic ocular muscles, are the seven extrinsic muscles of the eye in humans and other animals. Six of these muscles control eye movement, while the seventh, the levator palpebrae superioris, controls eyelid elevation. The six muscles responsible for eye movement are the four recti muscles and the superior and inferior oblique muscles. The recti muscles are named according to their relative positions of attachment: the superior rectus muscle, lateral rectus muscle, medial rectus muscle, and inferior rectus muscle. The superior rectus muscle originates from the upper part of the annulus of Zinn, a common tendinous ring lying in the back of the orbit. The medial rectus is the muscle closest to the nose. The superior and inferior recti also pull the eye medially, causing it to roll with contraction. The two oblique muscles are the inferior oblique muscle and the superior oblique muscle. The inferior oblique originates at the lower front of the nasal orbital wall and pulls the eye upward and laterally.
The extraocular muscles are the most specialised skeletal muscles in the human body, with a large ratio of nerve fibres to skeletal muscle fibres. They are broadly divided into voluntary and involuntary muscles. The voluntary muscles include the six muscles that control eye movement and the levator palpebrae superioris, which raises the upper eyelid. The involuntary muscle group includes the superior tarsal muscle (Muller's muscle), inferior tarsal muscle, and orbitalis. The extraocular muscles develop alongside Tenon's capsule (part of the ligaments) and the fatty tissue of the eye socket (orbit). They are supplied mainly by branches of the ophthalmic artery, such as the muscular branches, the lacrimal artery, and the infraorbital artery.
The actions of the six muscles responsible for eye movement depend on the position of the eye at the time of muscle contraction. Eye movements must be precise and fast, such as when reading, where the reader must shift their gaze constantly. While most eye movement is accomplished without conscious effort, it is under voluntary control. The primary gaze is when the eyes are facing straight ahead. From this position, an action from an extraocular muscle produces a secondary or tertiary gaze. The rectus and oblique muscles are involved in the different gaze positions of the eye.
The extraocular muscles have a common site of origin in the Annulus of Zinn, located at the orbital apex. Each rectus and oblique muscle has a functional insertion point at the closest point where the muscle first contacts the globe, known as the arc of contact. The superior oblique muscle is an exception, as it is innervated by the trochlear nerve rather than the oculomotor nerve. The levator palpebrae superioris does not contact the globe directly but elevates the eyelid. The Whitnall ligament is formed where the connective tissue from the levator palpebrae superioris connects with similar tissue from the superior rectus.
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Infrahyoid muscles
The infrahyoid muscles are a group of four paired muscles located inferior to the hyoid bone in the neck. They are also referred to as "strap muscles". The four infrahyoid muscles are the omohyoid, sternothyroid, thyrohyoid, and sternohyoid muscles. These muscles, along with the suprahyoid muscle group, control the positioning of the hyoid bone and are important for several functions related to speech, swallowing, and the movement of the larynx.
The omohyoid muscle is composed of two bellies, superior and inferior, which are connected by a muscular tendon. The superior belly arises from the hyoid bone, while the inferior belly arises from the scapula. The two bellies are connected by an intermediate tendon, which is anchored to the clavicle by the deep cervical fascia. The omohyoid muscle can be absent or double, and it may be attached directly to the clavicle. It is supplied by the superior thyroid and lingual arteries. The omohyoid depresses the hyoid bone and tenses the lower part of the deep cervical fascia during prolonged inhalation efforts, reducing the tendency for soft parts to be sucked inward. Additionally, due to its attachment to the carotid sheath, the omohyoid maintains a low pressure in the internal jugular vein, increasing the blood return from the head to the superior vena cava.
The sternohyoid muscle is the most superficial of all the infrahyoid muscles. It originates from the sternum and sternoclavicular joint and ascends to insert onto the hyoid bone. The sternohyoid muscle functions to depress the hyoid bone and is innervated by the anterior rami of C1-C3, carried by a branch of the ansa cervicalis.
The sternothyroid muscle is located underneath the sternohyoid in the deep plane of the neck. It arises from the manubrium of the sternum and attaches to the thyroid cartilage. This muscle depresses the thyroid cartilage and is innervated by the anterior rami of C1-C3, carried by a branch of the ansa cervicalis.
The thyrohyoid muscle is a short band of muscle thought to be a continuation of the sternothyroid. It originates at the oblique line of thyroid cartilage and inserts onto the hyoid bone. Unlike the other infrahyoid muscles, the thyrohyoid is not innervated by the ansa cervicalis but rather by nerve fibers from the anterior ramus of spinal nerve C1, which reaches the muscle via the hypoglossal nerve. The thyrohyoid has two functions: it depresses the hyoid bone in conjunction with the other infrahyoid muscles, and it elevates the larynx if the hyoid bone is stabilized by the suprahyoid muscles.
Damage to the ansa cervicalis, which innervates most of the infrahyoid muscles, can result in paresis or paralysis of the infrahyoid muscles. This can manifest as swallowing difficulties, a hoarse voice, and throat tightness.
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Frequently asked questions
The muscles of the head and neck are responsible for several important tasks, including movement of the head and neck, chewing, swallowing, speech, facial expressions, and movement of the eyes.
The masseters, temporalis, medial pterygoid, and lateral pterygoid are associated with jaw movements and receive motor innervation from the mandibular nerve.
The extra-ocular muscles control the movements of the eyeball and superior eyelid. There are six muscles involved in controlling eyeball movements: superior, inferior, medial, and lateral recti muscles, as well as the superior and inferior oblique muscles.
The neck muscles, including the sternocleidomastoid and trapezius, are responsible for the gross motor movements of the head and neck. The buccinator muscles, found on each side of the face, compress the cheeks and enable functions like whistling, blowing, and sucking. The occipitofrontalis muscle moves the scalp and eyebrows.
