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Carotid Triangle

Contents

Introduction

The carotid triangle is one of the natural geometrical formations of the neck. The triangle is located anterolaterally on each side of the neck. It is comprised of various anatomical structures that are noted as theoretical borders. They surround other groups of anatomical structures (mainly vessels) ascending and descending in order to supply and drain the head and neck.

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Borders

Each triangle has three sides which are known as borders. In this particular instance, the triangle happens to be a scalene triangle, where none of the sides are of equal length.

Carotid triangle (Posterior belly of digastric muscle) - lateral-right view

The posterior border which is the largest of the three sides or the base of the triangle is formed by the sternocleidomastoid muscle. Anteroinferiorly, the shortest side is composed of the omohyoid muscle and the anterosuperior border is limited by the posterior belly of the digastric muscle. The hyoid bone can be seen in the most anterior angle of the carotid triangle, with two of the three sides either originating or inserting upon it. Medially, the floor of the triangle is formed by parts of the thyrohyoid muscle, the hyoglossus muscle, and the middle and inferior pharyngeal constrictor muscles. It is covered laterally by the integument, the platysma, and the superficial and deep cervical fasciae.

Contents

As previously stated, the contents of the carotid triangle are made up of arteries, veins, and nerves. The points of interest are listed below according to the previously mentioned vessels.

Arteries

Of the arteries in the triangle, the common carotid is the largest where it bifurcates in the upper corner of the triangle into the internal and external carotid arteries. Other arterial branches visible in this space are branches of the external carotid artery:

  • the superior thyroid artery
  • the lingual artery
  • the facial artery
  • the occipital artery
  • the ascending pharyngeal artery

External carotid artery & branches - lateral-right view

Veins

As for the veins, all branches correspond to a previously mentioned artery where they all drain into the internal jugular vein. The latter runs laterally to the common carotid artery. The list of branches includes the:

  • superior thyroid vein
  • the lingual veins
  • common facial vein
  • occipital vein
  • ascending pharyngeal vein

Internal jugular vein - lateral-right view

Nerves

When relating to the nerves, an important structure must first be mentioned before the other descending cranial nerves: the carotid sheath. It is formed by the middle cervical fascia where it encompasses the vagus nerve (CN X) as well as the internal jugular vein, the common carotid artery, and deep cervical lymph nodes. Superficial to the carotid sheath, the hypoglossal nerve (CN XII) also descends within the triangle, as does the accessory nerve (CN XI), and the ansa cervicalis profunda.

Nerves of the carotid triangle (Sternocleidomastoid muscle) - ventral view

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Show references

References:

Author, Review and Layout:

  • Dr. Alexandra Sieroslawska
  • Francesca Salvador
  • Adrian Rad

Illustrators:

  • Carotid triangle (Posterior belly of digastric muscle) - lateral-right view - Paul Kim
  • External carotid artery & branches - lateral-right view - Paul Kim
  • Internal jugular vein - lateral-right view - Paul Kim
  • Nerves of the carotid triangle (Sternocleidomastoid muscle) - ventral view - Paul Kim
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