The Anatomy of the External Carotid Artery

The external carotid artery is a major artery of the head and neck

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One of the major sources of oxygen-rich blood to the head, the external carotid artery is the smaller of the two arteries that arise at the terminal end of the common carotid artery, near the upper border of the larynx at each side of the neck. On both sides, these arteries run upwards and slightly to the front, before curving backward to reach the space behind the upper portion of the mandible, or jawbone.

Since it plays such an essential role in supplying the brain, trauma or disease of the external carotid artery can lead to very serious consequences. Rupture due to an injury can lead to permanent disability or death. Carotid artery disease, due to partial or total blockage of blood flow, is the leading cause of stroke

Anatomy

One of the two terminal branches of the common carotid artery, the external carotid arises at the upper border of the thyroid cartilage in the larynx around the fourth vertebra of the neck.

From there it climbs upwards angling forward slightly, before angling back to reach the space behind the “neck” of the mandible—the upper rear of the jawbone. There it accesses the parotid gland, the source for saliva, where it terminates into the superficial temporal and maxillary arteries.

As the external carotid artery runs its course from the middle of the neck to the space behind the upper mandible, it becomes progressively smaller and gives off a number of branches.

The branches of the external carotid artery include:

  • Superior thyroid artery: The origin of the super laryngeal artery, which supplies the larynx, the superior thyroid artery delivers blood to important structures like the thyroid gland, as well as the muscles on the front of the neck.
  • Ascending pharyngeal artery: Ascending along the pharynx, the ascending pharyngeal artery supplies that region as well as the prevertebral muscles near the vertebrae in the neck.
  • Lingual artery: A primary source of blood to the tongue and bottom of the mouth, this branch is covered by the hypoglossal nerve, which delivers signals to and from that area. It supplies important muscles in the tongue. 
  • Facial artery: Running from the middle of the mandible into the face, this branch supplies the tonsils, the palate, and the submandibular glands, another major source of saliva.
  • Occipital artery: This branch supplies the rear region of the scalp and accesses the base of the skull.
  • Posterior auricular artery: This branch, running behind important structures of the auditory system, is tasked with delivering blood to parts of the ear as well as the adjacent musculature, parotid gland, facial nerve, and scalp.
  • Superficial temporal artery: The smaller of the two terminal branches of the external carotid, this artery supplies the temporal region in the back of the scalp.
  • Maxillary artery: An essential branch delivering blood to a number of regions, including the dura mater (the membrane surrounding the brain), the mandible, the teeth, as well as a number of facial muscles, this is the larger of the two terminal branches.

Anatomical Variations

Variations in the structure of the external carotid artery occur most often at its origin, where doctors have seen the external carotid artery emerge lower (at the cricoid cartilage) or higher (at the hyoid bone).

In addition, branching patterns can also vary. These include:

  • Linguofacial trunk: A common origin of the lingual and facial arteries, this occurs in about 20% of cases.
  • Thyrolingual trunk: This is when the superior thyroid and lingual arteries arise at the same location and occurs in about 2.5% of cases.
  • Thyrolinguofacial trunk: About 2.5% of the time there’s a common origin of the thyroid, lingual, and facial arteries.
  • Common occipito-auricular trunk: In 12.5% of cases, the occipital and posterior arteries share an origin.

Function

Along with the internal carotid artery, this vessel is a major supplier of blood to the head and neck. As such, and along with its many branches, it plays an essential role in delivering oxygenated blood to the face, scalp, tongue, upper and lower teeth, gums, sinus, external and middle ear, pharynx, larynx, as well as the thyroid.

Clinical Significance

Given the essential nature of this artery system, disease or trauma to this artery can have serious consequences.

Blockages of this vessel due to the build-up of fatty deposits (plaques)—a condition called atherosclerosis—leads to carotid artery disease. This affects the amount of oxygen that reaches the brain and is a leading cause of stroke, a “brain attack” in which there is rapid neuron (brain cell) death. This medical emergency can lead to long-term disability such as loss of speech and partial paralysis, as well as death.

In addition, damage to the external carotid artery due to head injury can lead to an aneurysm, a ballooning of a portion of the artery, or complete rupture of this essential vessel. This, too, can become very serious and can rapidly lead to death or permanent disability.

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