THE ANTERIOR TRIANGLE OF THE NECK

Using a simplified lateral view of the neck we can easily identify the Borders of the anterior triangle of the neck:

  • Midline of the neck from chin to manubrium
  • Posterior border of the sternocleidomastoid
  • Inferior border of the mandible

The Investing layer of deep cervical fascia anteriorly covers the anterior triangle of the neck and fuses with the opposite fascia in the midline.

 

Contains the Suprahyoid and the Infrahyoid muscles:

Suprahyoid:

Mylohyoid*

Digastric-Ant*

Digastric-Post**

Stylohyoid**

Geniohyoid***

Infrahyoid:

Sternohyoid A

Sternothyroid A

Omohyoid-Inf A (actually in the posterior triangle but included here for the sake of comparison)

Omohyoid-Sup A

Thyrohyoid***

Innervation: A = Ansa Cervicalis (c1, c2, c3) **=Facial Nerve
  * =Mylohyoid Nerve from the Inferior Alveolar Nerve of V3 *** = c1
Origins, Insertions and Actions can be reviewed in the text.

The anterior triangle of the neck can be further subdivided into:

Submental Triangle: between the anterior belly of the digastric, superior to the hyoid bone, and the midline of the neck

Submandibular (Digastric) Triangle: between the posterior and anterior bellies of the digastric muscle and inferior border of the mandible. Its floor is formed by the mylohyoid, hyoglossus and middle constrictor muscles.

Muscular Triangle: between the superior belly of the omohyoid, lower anterior margin of the sternocleidomastoid and the median line of the neck.

Medially contains infrahyoid muscles.

Carotid Triangle: between the posterior belly of the digastric, superior belly of the omohyoid and deep to the sternocleidomastoid muscle.

As the vascular area of the neck, it is most noted for the carotid sheath and its contents:

Common Carotid Artery

Internal Jugular Vein

Vagus N

The Common Carotid Artery arises in the base of the neck from the brachiocephalic artery on the right side and directly from the arch of the aorta on the left side in the superior mediastinum of the thorax. It passes into the base of the neck through the thoracic inlet bounded by T1 vertebral body, the sternum and first rib and ascends into the carotid triangle

Internal:
The carotid sinus and body are for mechanisms controlling blood pressure.
External:

Branches of the External Carotid Artery can be described through SALFOP | S-MAX

Superior thyroid artery (I) arises close to the carotid bifurcation. It descends anteriorly across the triangle to enter the superior pole of the thyroid gland anastomosing with its opposite counterpart and the inferior thyroid artery. Its branches are:

Location Tip: Seen running with the internal laryngeal nerve piercing thyrohyoid membrane

Ascending pharyngeal artery (I) arising near the carotid bifurcation from the posterior surface of the external carotid and passing posteriorly to the back of the pharynx. It supplies the pharyngeal constrictor muscles (lateral wall of the pharynx and the nasopharynx) and gives off small branches that supply the prevertebral muscles, middle ear and meninges, tonsil (palatine)

Lingual artery (DI) passes superiorly deep to the suprahyoid muscles to enter and supply the tongue. It also gives branches to the suprahyoid muscles and the sublingual gland (tonsil)

Facial artery (D) arises Immediately above the level of the hyoid bone and dips into the digastric triangle and around the submandibular gland. It ascends and crosses over mandible to supply the anteromedial aspect of the face (incl. lips, nose). It also sends branches to the palatine tonsil (tonsillar br.), the submandibular gland and on the face, to both the lips and the nose. It ends as the angular artery which anastamoses with the infraorbital

Occipital artery (D) arises on posterior side of ext. carotid, opposite facial artery, above the ascending pharyngeal, sends branches to the SCM, the dura mater, and then courses to the back of the head to supply the scalp

Location Tip: found by identifying the hypoglossal nerve (CN XII) which loops around it from posterior to anterior.

Posterior Auricular (S) courses behind the external ear and helps to supply the scalp, the middle ear, and the auricle. Neuritis of CNVII might be due to compression of this artery due to proximity to the nerve. In general, palsy of CNVII is termed Bell's palsy.

Superficial Temporal (S) Large terminal branch arising opposite external auditory meatus supplying the scalp on the lateral side of the head and giving off the transverse facial artery which courses across the face. Splits into parietal and temporal branches(Temporalis m.)

Maxillary artery (S) second large terminal branch, is the principal artery of the deep face. It has 3 divisions and many branches in each division. It supplies the tympanic membrane, gives rise to the middle meningeal artery, supplies the muscles of mastication, all lower and some upper teeth, the infraorbital region, the hard and soft palate, and the walls of the nasal cavity. More information regarding the maxillary artery can be found in its dedicated section.

                                                                 
Branches of the External Carotid Artery can also be described using the following diagram:

Note how the structures are physically placed - which ones are posterior, anterior, etc- and use that as a guide not only for locating them on the cadaver, but also for memorizing the structures themselves.

Internal Jugular Vein collects blood from the brain, face and neck

Vagus nerve (CNX)

The vagus has an extensive distribution as it conveys voluntary motor and sensory nerve fibers to structures in the neck, and viscero-motor fibers to thorax and abdomen. It enters the neck by exiting the skull through the jugular foramen. In the carotid triangle it lies behind and between the carotid and jugular vessels. Several branches are present.

A pharyngeal branch passes between the internal and external carotid vessels to the middle constrictor of the pharynx to join branches from the glossopharygeal nerve to form the pharyngeal plexus.

A superior laryngeal nerve arises below the pharyngeal branch and passes to the side of the larynx deep to both External and Internal Carotid Arteries.

The superior laryngeal nerve from X divides into:

Outside the triangle the important recurrent laryngeal branches arise.

Other branches in the neck region include:

Ansa Cervicalis

Sympathetic Trunk Autonomic Nerve Fibers and Ganglia

Inferior: At the level of the 1st rib/C7

Middle: At the level of cricoid cartilage (C6)/Inferior thryoid artery Superior: At the level of C1/C2, Largest