The carotid triangle is one of the geometrical anatomical formations of the neck. It is comprised of various anatomical structures that are noted as theoretical borders which surround other groups of anatomical structures (mainly vessels) ascending and descending in order to supply the head and neck.
Every triangle has three sides and therefore these sides are to be known as borders. In this particular instance, the triangle happens to be a scalene triangle, where none of the sides are of equal length. The posterior border which is the largest of the three sides or the base of the triangle is formed by the sternocleidomastoid muscle. Inferiorly, the shortest side is composed of the omohyoid muscle and the superior 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, superficial cervical fascia, the platysma and deep cervical fascia.
The contents of the carotid triangle is made up of arteries, veins and nerves. The branches of interest will be listed below according the previously mentioned types of vessels.
Of the arteries, the common carotid is by far the largest and it bifurcates in the upper corner of the triangle, into the internal carotid artery and external carotid artery. All the other arterial branches visible in this space a branches of the external carotid artery and include the superior thyroid artery, the lingual artery, the facial artery, the occipital artery and the ascending pharyngeal artery.
As for the veins, all the branches correspond to a previously mentioned artery and they all drain into the internal jugular vein, which runs laterally to the common carotid artery. The list includes the superior thyroid vein, the lingual veins, the common facial vein, the ascending pharyngeal vein and the occipital vein.
When relating to the nerves, the most important structure must first be mentioned before the other descending cranial nerves. The carotid sheath which is formed by the middle cervical fascia, encompasses the vagus nerve (CN X) as well as the internal jugular vein and the common carotid artery. The hypoglossal nerve (CN XII) also descends within the triangle, as does the accessory nerve (CN XI) and the ansa cervicalis profunda.