The external carotid artery is a large blood vessel responsible for delivering blood to the neck and head. Arising from the common carotid artery, which branches off from the aorta via the brachiocephalic artery, it originates high in the neck and runs up the side of the jaw toward the front of the earlobe. Like the internal carotid artery, which also branches off from the common carotid, the external carotid artery brings oxygenated, nutrient-rich blood from the heart and lungs to structures in the neck like the thyroid and larynx, to the face, and to the cranium.
This vessel splits off from the common carotid artery near the top of the thyroid cartilage or Adam’s apple, aligning with the ear on either side of the neck. From here it ascends, curves slightly forward, and then, as it approaches the curve of the mandible or jawbone, turns slightly backward. After passing vertically behind the mandible and reaching the point where the earlobe meets the jawbone, the external carotid artery divides into two new arteries, the superficial temporal and maxillary arteries. This division occurs within the parotid gland, the large salivary gland situated to either end of the jawbone. The superficial temporal artery goes on to supply blood to the cranium and is visible in the temples, while the maxillary artery curves forward to bring blood to the face.
Relevant to doctors, emergency medical technicians (EMTs), and other practitioners of cardiopulmonary resuscitation (CPR), the external carotid artery is the blood vessel that is often manually palpated to determine if an individual has a pulse. This vessel is the preferred point on the body for measuring pulse largely due to its proximity to the surface of the skin and accessibility—it is rarely obstructed by clothing or other objects. In addition to the skin the external carotid is layered beneath subcutaneous body fat, if present, the platymus and sternocleidomastoid muscles, and the fascia or fibrous tissue encasing these muscles. No bones, cartilage, or organs block access to this artery.
A few structures do cross the external carotid artery at some point along its length. These include the narrow stylohyoideus and digastricus muscles, which cross the neck obliquely under the jaw, the hypoglossal nerve, which innervates the tongue, and several veins exiting the head and neck. In addition, several new arteries branch off the artery along its length before it terminates, vessels like the superior thyroid, lingual, facial, ascending pharyngeal, occipital, and posterior auricular arteries, which transport oxygen-rich blood to the thyroid, larynx, face, throat, skull, and ears, respectively.