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Triangles of the Neck

Trigona colli

For medical students2 min readUpdated 2026-10-10

The triangles of the neck are topographic and anatomical regions designated to facilitate clinical study and surgical orientation. The sternocleidomastoid muscle serves as the primary landmark, dividing the neck into two large zones: the anterior and posterior triangles, each of which is further subdivided into smaller triangles.

Primary LandmarkThe sternocleidomastoid muscle (m. sternocleidomastoideus) forms the boundary between the anterior and posterior regions.
Anterior RegionContains four smaller triangles that house critical neurovascular bundles.
Carotid TriangleThe anatomical site projecting the common carotid artery and its bifurcation.
Posterior RegionContains the brachial and cervical plexuses and is subdivided into two smaller zones.

Anterior Triangle of the Neck

Overall, the anterior triangle represents a broad region defined by three distinct borders:

For precise topographical description, this area is subdivided into 4 smaller triangles, with three being clinically prominent.

1. Submental Triangle (trigonum submentale)

Located in the highest part of the neck. Its borders are formed by the anterior bellies of the digastric muscle (m. digastricus) bilaterally, with the body of the hyoid bone forming its base. The primary structures within this area are lymph nodes.

2. Submandibular Triangle (trigonum submandibulare)

This region is bounded by the inferior border of the mandible and the anterior and posterior bellies of the m. digastricus. It contains the submandibular salivary gland and the facial vessels.

3. Carotid Triangle (trigonum caroticum)

A critical anatomical region named after the major vessels passing through it.

Boundaries of the Carotid Triangle:

Contents: This triangle contains the common carotid artery (a. carotis communis) and its bifurcation (bifurcatio carotidis). Additionally, it houses the internal jugular vein (v. jugularis interna), vagus nerve (n. vagus), and the ansa cervicalis.

Posterior Triangle of the Neck

The posterior region of the neck is also triangular in shape. It is bounded anteriorly by the posterior border of the m. sternocleidomastoideus, posteriorly by the anterior border of the trapezius muscle (m. trapezius), and inferiorly by the clavicle.

The omohyoid muscle divides this large area into two smaller topographical zones.

Triangle NameLatin TermBoundaries and Contents
Omoclavicular (Subclavian)trigonum omoclaviculare (or supraclaviculare)Located between the inferior belly of the m. omohyoideus and the clavicle. Contains the subclavian artery (a. subclavia) and structures of the brachial plexus (plexus brachialis).
Omotrapezoidtrigonum omotrapezoideumLocated between the m. omohyoideus and m. trapezius. Contains branches of the cervical plexus (plexus cervicalis) and the accessory nerve (n. accessorius).

Frequently asked questions

What smaller triangles comprise the anterior triangle of the neck?

The anterior (medial) triangle of the neck comprises four smaller triangles:

  • Submental triangle (trigonum submentale) — unpaired, located in the suprahyoid region.
  • Submandibular triangle (trigonum submandibulare) — located above the hyoid bone.
  • Carotid triangle (trigonum caroticum) — located in the infrahyoid region.
  • Muscular (omotracheal) triangle (trigonum omotracheale) — also located below the hyoid bone.
What vessels and nerves form the contents of the carotid triangle?

The contents of the carotid triangle form the main neurovascular bundle of the neck and its branches:

  • Common carotid artery (a. carotis communis) — positioned medially, along with the carotid bifurcation (bifurcatio carotidis).
  • Internal jugular vein (v. jugularis interna) — positioned laterally.
  • Vagus nerve (n. vagus) — positioned between and posterior to the artery and vein.
  • Ansa cervicalis — formed superficially over the fascial sheath of the bundle.
What anatomical structures constitute the contents of the submandibular triangle?

The contents of the submandibular triangle include glandular, neurovascular, and lymphatic structures:

  • Submandibular salivary gland (gl. submandibularis) — situated within its own fascial compartment.
  • Facial artery and vein (a. et v. facialis) — course through the triangle.
  • Hypoglossal nerve (n. hypoglossus) — runs in the space between the floor muscles.
  • Lymph nodes (nodi lymphoidei submandibulares) — anterior, middle, and posterior groups.

Additionally, Pirogov's triangle, which contains the lingual artery and vein, is located within this area.

What are the boundaries of the muscular (omotracheal) triangle?

The boundaries of the muscular or omotracheal triangle (trigonum omotracheale) are formed by the following anatomical landmarks:

  • Superiorly — Inferior belly of the omohyoid muscle (m. omohyoideus).
  • Laterally — Anterior border of the sternocleidomastoid muscle (m. sternocleidomastoideus).
  • Medially — Midline of the neck.

Within these boundaries lie the thyroid gland, larynx, and trachea.

What vessels and nerves pass through the omoclavicular (subclavian) triangle?

The omoclavicular triangle (trigonum omoclaviculare) contains the following vascular and neural structures enclosed in a fascial sheath:

  • Subclavian artery (a. subclavia) — specifically its third part.
  • Brachial plexus (plexus brachialis) — represented by its supraclavicular part.

Topographically, the trunks of the brachial plexus lie superior and posterior to the subclavian vessel.

Where is Pirogov's triangle (lingual triangle) located and how is it bounded?

Pirogov's triangle is located within the submandibular triangle of the neck. Its boundaries are:

  • Superiorly — Hypoglossal nerve (n. hypoglossus).
  • Anteriorly — Posterior border of the mylohyoid muscle (m. mylohyoideus).
  • Inferiorly and posteriorly — Tendon of the posterior belly of the digastric muscle (m. digastricus).

The floor of the triangle is formed by the hyoglossus muscle (m. hyoglossus), deep to which lies the lingual artery.

Which muscles form the boundaries of the carotid triangle?

The carotid triangle is bounded by the posterior belly of the m. digastricus, the superior belly of the m. omohyoideus, and the anterior border of the m. sternocleidomastoideus.

Where is the submandibular gland located?

It is located within the submandibular triangle (trigonum submandibulare), which is enclosed between the mandible and the two bellies of the m. digastricus.

What structures pass through the omoclavicular triangle?

The omoclavicular (subclavian) triangle (trigonum omoclaviculare) contains the subclavian artery (a. subclavia) and the brachial plexus (plexus brachialis).

Which muscle acts as the shared boundary between the anterior and posterior triangles of the neck?

The sternocleidomastoid muscle (m. sternocleidomastoideus). Its anterior border delimits the anterior triangle, and its posterior border delimits the posterior triangle.

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