Learning Objectives:

By the end of this module, students will be able to:

• Explain the organization and distribution of the muscles of the neck.
• Identify the muscles of the anterior neck and explain their function in swallowing/vocalization.
• Identify the major arteries and veins of the neck and explain what tissues or regions are supplied or drained by the main branches.
• Define the triangles of the neck and list the contents of each triangle

Terms to Know

The Neck Root of the neck Hyoid bone Superficial fascia Platysma Deep fascial layers Pretrachial fascia Prevertebral fascia Carotid sheath Prevertebral space Sternocleidomastoid Anterior, middle, and posterior scalenes Suprahyoid muscles Digastric Anterior belly Posterior belly Geniohyoid Stylohyoid Mylohyoid Infrahyoid muscles Omohyoid Sternohyoid Thyrohyoid Sternothyroid Anterior triangle Submental triangle Submandibular triangle Carotid triangle Muscular triangle Posterior triangle Occipital triangle Supraclavicular triangle

Vasculature of the Head and Neck Common carotid artery Internal carotid artery External carotid artery Superior thyroid artery Lingual artery Facial artery Occipital artery Maxillary artery Superficial temporal artery Vertebral artery Subclavian artery Superior sagittal sinus Transverse sinus Inferior sagittal sinus Straight sinus Sigmoid sinus Internal jugular vein External jugular vein Subclavian vein Brachiocephalic vein Superior Vena Cava

Muscles That Move the Head

The head, attached to the top of the vertebral column, is balanced, moved, and rotated by the neck muscles. When these muscles act unilaterally, the head rotates. When they contract bilaterally, the neck flexes or extends. The major muscle that laterally flexes and rotates the head is the sternocleidomastoid. In addition, both muscles working together are the flexors of the head. Place your fingers on both sides of the neck and turn your head to the left and to the right. You will feel the movement originate there. This muscle divides the neck into anterior and posterior triangles when viewed from the side.

 

Posterior and Lateral Views of the Neck

Muscles That Move the Head
Movement	Target motion direction	Prime mover	Origin	Insertion
Neck flexion, rotation, and lateral flexion	Individually: contralateral rotation; bilaterally: flexion	Sternocleidomastoid	Sternum; clavicle	Temporal bone (mastoid process); occipital bone
Neck flexion, lateral flexion, rib 1 & 2 elevation	Individually: lateral flexion; bilaterally: flexion, rib elevation	Anterior, Middle, Posterior Scalenes	Transverse process of cervical vertebra	1st and 2nd ribs
Neck extension and rotation	Individually: lateral flexion and ipsilateral rotation; bilaterally: extension	Semispinalis capitis	Transverse and articular processes of cervical and thoracic vertebra	Occipital bone
Neck extension, rotation, and lateral flexion	Individually: lateral flexion and ipsilateral rotation; bilaterally: extension	Splenius capitis	Spinous processes of cervical and thoracic vertebra	Temporal bone (mastoid process); occipital bone
Neck extension, rotation, and lateral flexion	Individually: lateral flexion and ipsilateral rotation; bilaterally: extension	Longissimus capitis	Transverse and articular processes of cervical and thoracic vertebra	Temporal bone (mastoid process)

Muscles of the Anterior Neck (Suprahyoid muscles and Infrahyoid muscles)

The muscles of the anterior neck assist in deglutition (swallowing) and speech by controlling the positions of the larynx (voice box), and the hyoid bone, a horseshoe-shaped bone that functions as a solid foundation on which the tongue can move. The muscles of the neck are categorized according to their position relative to the hyoid bone. Suprahyoid muscles are superior to it, and the infrahyoid muscles are located inferiorly.

 

Muscles of the Anterior Neck

 

The suprahyoid muscles elevate the hyoid bone, the floor of the mouth, and the larynx during deglutition. These include the digastric muscle, which has anterior and posterior bellies that work to elevate the hyoid bone and larynx when one swallows. The stylohyoid muscle moves the hyoid bone posteriorly, elevating the larynx, and the mylohyoid muscle lifts it and helps press the tongue to the top of the mouth. The geniohyoid depresses the mandible in addition to raising and pulling the hyoid bone anteriorly.

The strap-like infrahyoid muscles generally depress the hyoid bone and control the position of the larynx. The omohyoid muscle, which has superior and inferior bellies, depresses the hyoid bone in conjunction with the sternohyoid and thyrohyoid muscles. The thyrohyoid muscle also elevates the larynx’s thyroid cartilage, whereas the sternothyroid depresses it to create different tones of voice.

Hyoid Bone

The hyoid bone is an independent bone that does not contact any other bone and thus is not part of the skull. It is a small U-shaped bone located in the upper neck near the level of the inferior mandible, with the tips of the “U” pointing posteriorly. The hyoid serves as the base for the tongue above and is attached to the larynx below and the pharynx posteriorly. The hyoid is held in position by a series of small muscles that attach to it either from above or below. These muscles act to move the hyoid up/down or forward/back. Movements of the hyoid are coordinated with movements of the tongue, larynx, and pharynx during swallowing and speaking.

Hyoid Bone

Triangles of the Neck

The triangles of the neck provide an anatomical reference for the location of the contents of the neck. The anterior triangle sits anterior to the sternocleidomastoid muscle and inferior to the mandible. The anterior triangle is subdivided into four smaller triangles, the submental triangle, submandibular triangle, carotid triangle, and muscular triangle. The posterior triangle sits posterior to the sternocleidomastoid muscle and on the lateral region of the neck. The posterior triangle is subdivided into two smaller triangles, the occipital triangle, and the supraclavicular triangle.

 

Arteries and Veins of the Neck

The arteries and veins of the neck are covered in Module 20 under “Blood Supply to the Brain.” A discussion of the arteries and veins in the head and neck also exists in the lecture videos in Canvas. Students should have an understanding of the location of the arteries and veins of the head and neck, what structures are supplied by the arteries, and which structures are drained by the veins.

Arteries of the Head and Neck

Veins of the Head and Neck

Blood from the brain and the superficial facial veins flow into each internal jugular vein. Blood from the more superficial portions of the head, scalp, and cranial regions, including the temporal vein and maxillary vein, flows into each external jugular vein. Although the external and internal jugular veins are separate vessels, there are anastomoses between them close to the thoracic region. Blood from the internal and external jugular veins empties into the subclavian vein.