Muscles of the Neck

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The neck - general overview | Main Anatomy Index | Neck Index | Triangles of the neck

Last updated 1 April 2006

Superficial Neck Muscles

The Platysma Muscle (p. 786)

This is a wide, think, subcutaneous sheet of striated muscle.
It is located in the superficial fascia.
It ascends to the face from the anterior part of the neck.
The platysma (G. a flat plate) covers the superior part of the anterior cervical triangle and the anteroinferior part of the posterior cervical triangle.
Its fibres blend superiorly with the facial muscles.

Inferior attachments: fascia and skin over the pectoralis major and deltoid muscles.
Superior attachments: inferior border of the mandible and skin of the lower face.
Innervation: cervical branch of the facial nerve (CN VII).

This thin muscle tenses the skin of the neck. It also draws the corners of the mouth inferiorly and assists in depressing the mandible.
Acting superiorly, it produces skin ridges in the neck, releasing the pressure of the skin on the underlying veins.
When the entire muscle contracts, it wrinkles the skin of the neck in an oblique direction and widens the mouth.

This is one of the muscles of facial expression that we use to express sadness, horror, or fright.

The Sternocleidomastoid Muscle (p. 786)

This muscle is a broad strap-like muscle that is the key to the neck.
It runs superolaterally from the sternum and clavicle to the lateral surface of the mastoid process.
This muscle divides the neck into the posterior and anterior triangles.
The sternocleidomastoid is crossed by the platysma and external jugular vein.
It covers the great vessels of the neck and the cervical plexus of nerves.

Inferior attachment: sternal head-by a rounded tendon, which is attached to the anterior surface of the manubrium of the sternum, lateral to the jugular notch, clavicular head-superior surface of the medial third of the clavicle.
Superior attachment: lateral surface of the mastoid process of the temporal bone and the lateral half of the superior nuchal line of the occipital bone.
Innervation: spinal root of the accessory nerve (CN XI) and branches of the second and third cervical nerves (C2 and C3).

Acting alone, the sternocleidomastoid muscle tilts the head to its own side by drawing the mastoid process inferiorly (it lateral flexes the neck and rotates it so the face is turned superiorly toward the opposite side).
Acting together, these muscles flex the neck (e.g. when raising the head from a pillow).

The Prevertebral Muscles

These deep anterior vertebral muscles are covered anterior by prevertebral fascia.
They all flex the neck and the head on the neck and are supplied by ventral primary rami of the cervical nerves.

The Longus Colli Muscle (p. 807)

This is the longest and most medial of the prevertebral muscles.
It extends from the anterior tubercle of the atlas to the body of T3 vertebra.
It is also attached to the bodies of the vertebrae between C1 and C3, and the transverse processes of C3 to C6 vertebrae.

The Longus Capitis Muscle (p. 807)

This is broad and thick superiorly, and arises from the anterior tubercles of C3 to C6 cervical transverse processes.
It is attached superiorly to the base of the skull, the basilar part of the occipital bone.

The Suprahyoid Muscles

This group of muscles is located superior to the hyoid bone and connects to this bone and the skull.
This group includes the mylohyoid, geniohyoid, stylohyoid and digastric muscles.

The Mylohyoid Muscles (p. 796)

These are thin, flat triangular muscles that form a sling inferior to the tongue.
They form the floor of the mouth.
The Greek word myle means "a mill" and denotes the role of these muscles in grinding the food in the mouth.

Superior attachment: mylohyoid line of mandible.
Inferior attachment: raphe and body of hyoid bone.
Innervation: mylohyoid nerve, a branch of the inferior alveolar nerve.

It elevates the hyoid bone, floor of the mouth and the tongue during swallowing and speaking.

Geniohyoid Muscles (p. 796)

These are short narrow muscles that contact each other in the median plane.
They are located superior to the mylohyoid muscles, where they reinforce the floor of the mouth.

Superior attachment: inferior mental spine of mandible.
Inferior attachment: body of hyoid bone.
Innervation: C1 via the hypoglossal nerve (CN XII).

It pulls the hyoid bone anterosuperiorly, and shortens the floor of the mouth and widens the pharynx.

The Stylohyoid Muscles (p. 796)

These muscles form a small slip on each side, which is nearly parallel to the posterior belly of the digastric muscle.

Superior attachment: styloid process of the temporal bone.
Inferior attachment: body of hyoid bone.
Innervation: cervical branch of facial nerve (CN VII).

It elevates and retracts the hyoid bone, thereby elongating the floor of the mouth.

The Digastric Muscles (p. 796)

Click here for a diagram of the the posterior belly of digastric muscle and its relations.

Each of the strap-like muscles has two bellies (G. gaster, belly) that descend toward the hyoid bone.
They are joined by an intermediate tendon that is connected to the body and the greater horn of the hyoid bone by a strong loop or sling of fibrous connective tissue.
This fibrous pulley allows the intermediate tendon to slide anteriorly and posteriorly.

Superior attachment: anterior belly-digastric fossa of mandible, posterior belly-mastoid notch of temporal bone.
Inferior attachment: intermediate tendon to body and greater horn of hyoid bone.
Innervation: anterior belly-mylohyoid nerve, a branch of the inferior alveolar nerve, posterior belly-facial nerve (CN VII).

It depresses the mandible and raises the hyoid bone. Also, it steadies the hyoid bone during swallowing and speaking.

The Infrahyoid Muscles

These muscles are often referred to as strap muscles due to their ribbon-like appearance.
They are located inferior to the hyoid bone.
These muscles anchor the hyoid bone and depress the hyoid and larynx during swallowing and speaking.

The Sternohyoid Muscle (p. 797)

This is a thin, narrow, strap muscle that is superficial except inferiorly where it is covered by the sternocleidomastoid muscle.

Inferior attachment: manubrium of sternum and medial end of clavicle.
Superior attachment: body of hyoid bone.
Innervation: C1, C2, C3 from ansa cervicalis.

It depresses the hyoid bone after it has been elevated during swallowing.
It also helps to steady the hyoid during movements of the tongue, larynx and pharynx.

The Sternothyroid Muscle (p. 797)

This is a thin muscle located deep to the sternohyoid muscle, and is shorter and wider than it.

Inferior attachment: posterior surface of manubrium of sternum.
Superior attachment: oblique line of thyroid cartilage.
Innervation: C2 and C3 by a branch of the ansa cervicalis.

It depresses the hyoid bone and larynx after it has been elevated by muscles during swallowing and vocal movements.
It also pulls the thyroid cartilage away from the hyoid bone, thereby opening the laryngeal orifice.

The Thyrohyoid Muscle (p. 797)

This muscle appears to be the superior continuation of the sternothyroid muscle.

Inferior attachment: oblique line of thyroid cartilage.
Superior attachment: inferior body of body and greater horn of hyoid bone.
Innervation: C1 via hypoglossal nerve (CN XII).

It depresses the hyoid bone and elevates the larynx.
It is mainly responsible for preventing food from entering the larynx during swallowing (it pulls the larynx and hyoid bone together)..

The Omohyoid Muscle (p. 797)

This muscle has two bellies that are united by an intermediate tendon, which is connected to the clavicle by a fascial sling.
The omohyoid muscle is an important landmark in the neck because it divides the anterior and posterior triangles into smaller triangles.

Inferior attachment: superior border of scapula near the suprascapular notch.
Superior attachment: inferior border of hyoid bone.
Innervation: C1, C2, C3 by a branch of ansa cervicalis.

It depresses, retracts and steadies the hyoid during swallowing and speaking.

The Scalene Muscles

The Scalenus Anterior Muscle (p. 654, Snell 5^th ed.)

The scalenus anterior muscle is a key muscle of the root of the neck.
It is deeply placed and descends almost vertically from the vertebral column to the first rib.

Origin: from the anterior tubercles of the transverse processes of C3-6.
Insertion: the fibres pass downward and laterally, to be inserted into the scalene tubercle on the inner border of the first rib.
Innervation: from the anterior rami of C4, C5, C6.

It assists in the elevating of the first rib.
When acting from below, it laterally flexes and rotates the cervical part of the vertebral column.

Relations

Anteriorly: the prevertebral layer of deep cervical fascia, which binds the phrenic nerve down to the anterior surface of the muscle; the superficial cervical and suprascapular arteries, which cross the phrenic nerve; and the internal jugular and subclavian veins.

Posterior: the subclavian artery, brachial plexus, and cervical dome of the pleura.

Medially: the vertebral artery and vein, inferior thyroid artery, thyrocervical trunk, sympathetic trunk, and on the left side, the thoracic duct.

Laterally: the roots of the phrenic nerve unite at the lateral border of the muscle at the level of the cricoid cartilage, before the nerve starts to descend on its anterior surface. The roots of the brachial plexus and subclavian artery emerge from behind the lateral border of the muscle, to enter the posterior triangle of the neck.

The Scalenus Medius Muscle (pp. 654-5, Snell 5^th ed.)

Origin: from the transverse process of the atlas and posterior tubercles of the transverse processes of the next five cervical vertebrae.
Insertion: the muscle passes downward and laterally and is inserted into the upper surface of the first rib, behind the groove for the subclavian artery. The muscle lies behind the roots of the brachial plexus and behind the subclavian artery.
Innervation: branches from the anterior rami of the cervical nerves.

It assists in elevating the first rib.
When acting from below it laterally flexes and rotates the cervical part of the vertebral column.

The Scalenus Posterior Muscle (p. 655, Snell 5^th ed.)

The scalenus posterior muscle may be absent or blended with the scalenus medius.

Origin: from the posterior tubercles of the transverse processes of the lower cervical vertebrae.
Insertion: it is inserted into the outer surface of the second rib.
Innervation: branches from the anterior rami of the lower cervical nerves.

It elevates the second rib.
When active from below, it laterally flexes the cervical part of the vertebral column.