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Superficial structures of the neck: Anterior triangle

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Figure 1: Borders and subdivisions of the anterior triangle of the neck, anterior view. A. Borders of the anterior triangle and its subdivisions. B. Contents of the submental triangle and submandibular triangle, anterior view. C. Nerves traveling through the submandibular triangle, lateral view. D. Contents of the carotid triangle.

Figure 2: Anatomy of the carotid arteries and the carotid body, anterior view.

Figure 3: Muscles of the anterior neck, anterior view. A. Superficial muscles. B. Deep muscles.

Figure 4: Arteries of the anterior neck, lateral view.

Figure 5: Veins of the anterior neck, lateral view.

Muscle	Origin	Insertion	Innervation	Action
Mylohyoid muscle	Mylohyoid line of the mandible	Mylohyoid raphe Body of the hyoid	Nerve to mylohyoid (CN V3)	Elevates the hyoid, the floor of the mouth and the tongue during speaking and swallowing
Geniohyoid muscle	Inferior mental spine of the mandible	Body of the hyoid	C1 via hypoglossal nerve (CN XII)	Pulls the hyoid antero-superiorly Shortens the floor of the mouth Widens the pharynx
Stylohyoid muscle	Styloid process of temporal bone	Attaches to the hyoid body	Stylohyoid branch of the facial nerve (CN VII)	Elevates and retracts the hyoid
Digastric muscle	Anterior belly Digastric fossa of the mandible Posterior belly Mastoid notch of the temporal bone	Body and greater horn of the hyoid bone via intermediate tendon of the digastric	Anterior belly Nerve to mylohyoid (CN V3) Posterior belly Digastric branch of the facial nerve (CN VII)	Depress the mandible against resistance Elevates and steadies the hyoid during swallowing and speaking
Sternohyoid muscle	Manubrium of the sternum Medial end of the clavicle	Hyoid body	C1-C3 via ansa cervicalis	Depresses the hyoid after elevation during swallowing
Omohyoid muscle	Superior border of the scapula	Inferior border of hyoid	C1-C3 via ansa cervicalis	Depresses, retracts and steadies the hyoid.
Sternohyoid muscle	Posterior surface of the manubrium	Oblique line of thyroid cartilage	C2 and C3 via ansa cervicalis	Depresses the hyoid and larynx
Thyrohyoid muscle	Oblique line of thyroid cartilage	Inferior border of the body and greater horn of the hyoid	C1 via the hypoglossal nerve (CN XII)	Depresses the hyoid Elevates the larynx

The neck is the anatomical region between the base of the cranium superiorly and the clavicles inferiorly and it joins the head to the trunk and limbs, serving as a major conduit for structures passing between them.

The neck is divided in two major triangles: anterior and posterior, based mainly on the borders of the sternocleidomastoid, or SCM, and trapezius muscles, as well as other muscular and bony structures found in the neck.

These regions provide a clear location regarding the structures, injuries or pathologies involving the neck. Now, the anterior triangle, like any respectable triangle, has three sides, called boundaries.

The anterior boundary is formed by the median line of the neck, the posterior boundary is formed by the anterior border of the sternocleidomastoid muscle, or SCM for short, and the superior boundary is formed by the inferior border of the mandible.

The triangle has a superficial boundary or a roof formed by subcutaneous tissue containing the platysma, a deep boundary or a floor formed by the pharynx, larynx and thyroid gland and an apex located at the jugular notch in the manubrium.

And if that wasn’t enough, the anterior triangle is further subdivided by the omohyoid and digastric muscles into four smaller triangles: submental, submandibular, carotid and muscular.

The submental triangle sits right below the chin and contains several small submental lymph nodes and small veins that unite to form the anterior jugular vein.

Inferiorly, the submental triangle is bounded by the hyoid body, and laterally by the right and left anterior bellies of the digastric muscles.

Summary

The anterior neck triangle, or just the anterior triangle, is a region of the neck bounded by the inferior border of the mandible superiorly, the anterior border of the sternocleidomastoid laterally, and the sagittal line down the midline of the neck medially.

The anterior triangle is home to several muscles, nerves, arteries, veins, and lymph nodes. Muscles of this region are in two groups: the suprahyoid and infrahyoid muscles. The suprahyoid muscles include the stylohyoid, the digastric, the mylohyoid, and the geniohyoid muscles. The infrahyoid muscles include the omohyoid, the sternohyoid, the thyrohyoid, and the sternothyroid muscles.

Nerves found in the anterior triangle include several cranial nerves, such as CN VII, CN IX, CNX, CN XI, and CN XII. Blood vessels passing through this region include the common carotid artery, which splits into the internal and the external carotid artery supplying various structures in the head. There is also the internal jugular vein, which drains venous blood from the head and neck.

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Superficial structures of the neck: Anterior triangle

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