Blood Supply of Mouth and Pharynx
The external carotid artery and its branches are responsible for essentially the total arterial supply of the mouth and pharynx. The common carotid artery, arising from the brachiocephalic trunk on the right and the arch of the aorta on the left, bifurcates at the level of the superior border of the thyroid cartilage into external and internal carotid arteries. From here the external carotid artery courses superiorly to a point posterior to the neck of the mandible, dividing in the substance of the parotid gland into the maxillary and superficial temporal arteries. The parotid gland surrounds part of the external carotid artery and the beginnings of its terminal branches. The gland gets many small branches from these vessels in its substance.
Five of the branches of the external carotid artery are involved in the supply of the mouth and pharynx. The superior thyroid artery leaves the anterior aspect of the external carotid near its beginning and courses inferiorly and anteriorly on the external surface of the inferior pharyngeal constrictor muscle, passing deep to the sternohyoid and omohyoid muscles to ramify on the anterolateral surface of the thyroid gland. Near its origin, the superior laryngeal artery pierces the thyrohyoid membrane to supply the tissues of the larynx. The lingual artery arises from the anterior surface of the external carotid, a short distance superior to the superior thyroid artery, opposite the tip of the greater horn of the hyoid bone. It courses anteriorly and slightly superiorly deep to the stylohyoid muscle, the posterior belly of the digastric muscle, and the hypoglossal nerve, and then passes medial to the hyoglossus muscle along the superior border of the greater horn of the hyoid. The facial artery, coming from the anterior aspect of the external carotid slightly superior to the lingual, is tortuous throughout its length to allow for movements of the head and of the lower jaw. It courses anteriorly and superiorly deep to the digastric and stylohyoid muscles sheltered by the mandible, lies in a groove on the submandibular gland, and then curves superiorly around the inferior border of the mandible near the anterior margin of the masseter muscle. From here it runs anteriorly and superiorly across the cheek and along the side of the nose, to end as the angular artery at the medial angle of the eye. The maxillary artery, the larger of the two terminal branches of the external carotid, passes anteriorly between the ramus of the mandible and the sphenomandibular ligament (first part), and continues anteriorly either deep or superficial to the lateral pterygoid muscle (second part), between the two heads of which it dips to reach the pterygopalatine fossa (third part). The infraorbital artery, which is a continuation of the maxillary, courses through the infraorbital canal of the maxilla to end in terminal branches on the face as it leaves the infraorbital foramen. The ascending pharyngeal artery arises from the posteromedial aspect of the external carotid very near its beginning. From here it ascends vertically between the internal carotid artery and the posterolateral aspect of the pharynx, to go as high as the undersurface of the base of the skull.
The lips, which are very vascular, are supplied chiefly by the superior and inferior labial branches of the facial artery, each of which courses from near the angle of the mouth, where they arise, toward the midline of each respective lip to meet the one on the opposite side. For the most part, they lie between the orbicularis oris muscle and the mucous membrane related to its inner surface. The mental branch of the inferior alveolar artery, a branch of the first part of the maxillary artery, anastomoses with the inferior labial artery, and the labial branch of the infraorbital artery anastomoses with the superior labial artery.
The cheek receives much of its arterial supply by way of the buccal artery, which springs from the second part of the maxillary artery and runs anteroinferiorly on the external surface of the buccinator muscle.
The arterial supply of the superior arcade of teeth, their alveolar processes, and gums is furnished in the artery, which arises from the second part of the maxillary artery. It courses inferiorly in the pterygopalatine fossa to divide into several small branches, most of which enter small foramina on the posterior aspect of the maxilla. The anterior and less constant middle superior alveolar branches of the infraorbital artery pass along the wall of the maxillary sinus to supply the rest of the upper jaw.
The inferior arcade of the teeth with the related bone and gums are supplied by the inferior alveolar artery. It enters the mandibular foramen to course in the alveolar canal and ends as the mental artery, which gives off an incisive branch before exiting through the mental foramen to supply the chin.
The arterial supply of the tongue is, for the most part, by way of the lingual artery. The anastomoses between the branches of the right and left lingual arteries are of a small enough caliber so that ligation of one artery makes that side of the tongue sufficiently bloodless for an operative procedure. Under cover of the posterior border of the hyoglossus muscle, the lingual artery gives off dorsal lingual branches, which travel superiorly and medial to the styloglossus muscle to supply the mucous membrane of the dorsum as far back as the epiglottis, anastomosing with other vessels supplying the tonsil. The portion of the artery from the anterior border of the hyoglossus forward to the tip of the tongue is the deep lingual artery, which lies deep to the genioglossus muscle and is under cover of the mucous membrane on the inferior surface of the tongue.
The mucous membrane of the floor of the mouth and the sublingual gland receive blood through the sublingual artery, which branches from the lingual near the anterior border of the hyoglossus muscle and courses anterior and superior to the mylohyoid muscle and lateral to the genioglossus. The muscles of the floor of the mouth are supplied by the submental branch of the facial artery and the mylohyoid branch coming off from the inferior alveolar just before it enters the mandibular foramen. These two arteries contribute some blood to the submandibular gland, which gets most of its supply from the nearby facial artery.
The arterial supply of the palate is chiefly from the descending palatine branch of the third part of the maxillary artery, which travels interiorly through the pterygopalatine canal to emerge from the greater palatine foramen and then courses anterior, medial to the alveolar process, to anastomose at the incisive foramen with a septal branch of the sphenopalatine artery. The lesser palatine artery, which runs posteriorly from the descending palatine at the greater palatine foramen, supplies the soft palate and anastomoses with other arteries that supply the tonsil. Anastomoses exist also with a palatine branch of the ascending pharyngeal artery, the dorsal lingual arteries, and the ascending palatine from the facial artery.
The muscles of mastication receive arterial twigs, named according to the muscle supplied, from the second part of the maxillary artery.
The pharynx receives blood from many sources, the amount from each source varying a great deal individually. One of the chief sources is the ascending pharyngeal artery, usually from the external carotid artery. Other arteries that run to the pharynx and can thus contribute to its supply are the ascending palatine and tonsillar branches of the facial artery, the superior thyroid artery and its superior laryngeal branch, and the inferior laryngeal and ascending cervical branches of the thyrocervical trunk from the subclavian artery. The pharyngeal branch of the third part of the facial artery passes through a bony canal to reach the roof of the pharynx, and the descending palatine artery, also from the third part of the facial, contributes to the supply in the region of the tonsil by its lesser palatine branches.