Module 22: Muscles and Triangles of the Neck

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
The left panel shows the lateral view of the neck. The middle panel shows the superficial neck muscles, and the right panel shows the deep neck muscles
The superficial and deep muscles of the neck are responsible for moving the head, cervical vertebrae, and scapulas.
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
This figure shows the front view of a person’s neck with the major muscle groups labeled.
The anterior muscles of the neck facilitate swallowing and speech. The suprahyoid muscles originate from above the hyoid bone in the chin region. The infrahyoid muscles originate below the hyoid bone in the lower 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
In this image, the location and structure of the hyoid bone are shown. The top panel shows a person’s face and neck, with the hyoid bone highlighted in grey. The middle panel shows the anterior view and the bottom panel shows the right anterior view.
The hyoid bone is located in the upper neck and does not join with any other bone. It provides attachments for muscles that act on the tongue, larynx, and pharynx.

 

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.

The image is a lateral view of the neck showing the triangles of the neck.
The triangles of the neck can provide a reference for the location of anatomical structures.

 

The image is a table defining the borders and contents of each triangle of the neck.
The borders and contents found in the triangles of the neck.

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.

This diagram shows the blood vessels in the head and brain.
Arteries Supplying the Head and Neck: The common carotid artery gives rise to the external and internal carotid arteries. The external carotid artery remains superficial and gives rise to many arteries of the head. The internal carotid artery reaches the brain via the carotid canal. The vertebral artery branches from the subclavian artery and passes through the transverse foramen in the cervical vertebrae.

Arteries of the Head and Neck

Major Arteries of the Head and Neck
Vessel Description
Brachiocephalic artery Single vessel located on the right side of the body; the first vessel branching from the aortic arch; gives rise to the right subclavian artery and the right common carotid artery; supplies blood to the head, neck, upper limb, and wall of the thoracic region
Subclavian artery The right subclavian artery arises from the brachiocephalic artery while the left subclavian artery arises from the aortic arch; gives rise to the internal thoracic, vertebral, and thyrocervical arteries; supplies blood to the arms, chest, shoulders, back, and central nervous system
Vertebral artery Arises from the subclavian artery and passes through the vertebral foramen through the foramen magnum to the brain; joins with the internal carotid artery to form the arterial circle; supplies blood to the brain and spinal cord
Common carotid artery The right common carotid artery arises from the brachiocephalic artery and the left common carotid artery arises from the aortic arch; each gives rise to the external and internal carotid arteries; supplies the respective sides of the head and neck
Internal carotid artery Arises from the common carotid artery and begins with the carotid sinus; goes through the carotid canal of the temporal bone to the base of the brain; combines with the branches of the vertebral artery, forming the arterial circle; supplies blood to the brain
External carotid artery Arises from the common carotid artery; supplies blood to numerous structures within the face, lower jaw, neck, esophagus, and larynx
Superior thyroid artery Arises from the external carotid artery; supplies blood to the thyroid
Lingual artery Arises from the external carotid artery; supplies blood to the tongue
Facial artery Arises from the external carotid artery; supplies the anterior face
Posterior auricular artery Arises from the external carotid artery; supplies the scalp behind the ear
Occipital artery Arises from the external carotid artery; supplies the occiput, posterior scalp
Maxillary artery Arises from the external carotid artery; supplies the cheek, muscles of mastication, the teeth, and nasal cavity
Superficial temporal artery Arises from the external carotid artery; supplies the lateral and superior scalp

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.

This diagram shows the veins present in the head and neck.
Veins of the Head and Neck: This left lateral view shows the veins of the head and neck, including the intercranial sinuses.
Major Veins of the Head and Neck  
Vessel Description
Internal Jugular Vein Parallel to the common carotid artery, which is more or less its counterpart, and passes through the jugular foramen and canal; primarily drains blood from the brain, receives the superficial facial vein, and empties into the subclavian vein
External Jugular Vein Drains blood from the more superficial portions of the head, scalp, and cranial regions, and leads to the subclavian vein
Temporal Vein Drains blood from the temporal region and flows into the external jugular vein
Facial Vein Drains blood from the anterior face, scalp, and nasal region and flows into the internal jugular vein
Maxillary Vein Drains blood from the maxillary region and flows into the external jugular vein

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