External carotid artery and its branches
The external carotid artery is one of the two main divisions of the common carotid artery. It stems from the aortic arch on the left side and from the brachiocephalic artery on the right side. it climbs the lateral sides of the neck within the carotid sheath, which is found just behind the sternocleidomastoid muscle. The carotid bifurcation occurs at the level of the thyroid cartilage in the larynx. The external carotid artery is the only division of the common carotid that gives branches to the neck region and supplies the external structures of the head and face.
Medially the hyoid bone, the wall of the pharynx, the superior laryngeal nerve and the parotid gland surround the artery. Laterally, the internal carotid artery passes by in the initial phase of the external carotid artery, along with the superior laryngeal nerve posteroinferiorly.
Posterosuperiorly however, the internal and external branches of the carotid are separated by the styloglossus muscle, the stylopharyngeus muscle, the glossopharyngeal nerve (CN IX), the pharyngeal branch of the vagus nerve (CN X) and part of the parotid gland. Anteriorly, the artery is covered by the skin, the superficial fascia, the platysma, the deep cervical fascia and the sternocleidomastoid muscle.
The nerves, vasculature and musculature that cross over the external carotid artery during its journey include the hypoglossal nerve (CN XII), the lingual nerve, the ranine nerve, the common facial nerve, the superior thyroid veins, the digastric muscle, the stylohyoid muscle, the parotid gland, the deep facial nerve, the temporal and internal maxillary veins.
The superior thyroid artery (S) is the origin of the superior laryngeal artery that supplies the larynx. The main artery also supplies the thyroid gland, infrahyoid muscles and the sternocleidomastoid muscle.
The ascending pharyngeal artery (A) ascends superiorly along the pharynx, while branching off to the pharynx, prevertebral muscles, the middle ear and the cranial meninges.
The lingual artery (L) is covered by the hypoglossal nerve (CN XII), the the stylohyoid muscle and the posterior belly of the digastric muscle. It runs beneath the hyoglossus muscles and branches into the deep lingual and sublingual arteries which supply the intrinsic muscles of the tongue and the floor of the mouth.
The occipital artery (O) supplies the posterior region of the scalp and grooves the base of the skull as it travels. Initially it passes deep to the posterior belly of the digastric muscle.
The posterior auricular artery (P) runs behind the external acoustic meatus and the mastoid process, separating the two structures. It supplies the adjacent musculature, the parotid gland, the facial nerve (CN VII), the ear and the scalp.
The maxillary artery (M) is the larger of the two terminal branches which can precede one another depending on which anatomist you ask. Its branches supply the external acoustic meatus, the tympanic membrane, the dura mater and the calvaria, the mandible, the gingivae, the teeth, the temporal muscle, the pterygoid muscle, the masseter muscle and the buccinator muscle.
The superficial temporal artery (S) supplies only the temporal region of the scalp, as it is the smaller terminal branch and does not have additional named branches or divisions.
If one looks back to the section of this article termed ‘Branches’, each major artery has been assigned a letter, which corresponds to the first letter of a word in each mnemonic. The order of arteries listed corresponds to the order they branch off from the external carotid artery as it ascends and follows the order of the words in each mnemonic. There are three different mnemonics, of which only one is needed in order to remember the branches.
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Carotid artery disease is a disorder of the common carotid artery or either of its main divisions. It occurs when plaque like growths start to form in these major arteries and limit the amount of blood that flows to the head and neck region. This ailment can become extremely serious, because it can cause ischemia to vital organs such as the brain and it also increases the risk of clot formation. The best way to treat and also avoid the buildup of arterial plaque is to minimize the risk of it forming in the first place by eating a healthy and well balanced diet, engaging in regular physical activity and avoiding situations where chronic stress is a major factor.