Blood Supply to the Head and Neck: Oral and Dental Significance

Core Review

Overview: Common Carotid Bifurcation

The common carotid arteries ascend in the neck within the carotid sheath (along with the internal jugular vein and vagus nerve). At approximately the level of the superior border of the thyroid cartilage (C3-C4 vertebral level), each common carotid bifurcates into the internal and external carotid arteries.

Internal carotid artery (ICA): Supplies the brain, orbit, and forehead. It has NO branches in the neck. The ICA enters the skull through the carotid canal in the petrous portion of the temporal bone. For the dental professional, the ICA is significant primarily as a landmark — the carotid sinus (baroreceptor, CN IX) and carotid body (chemoreceptor, CN IX and X) are located at the bifurcation and should be avoided during palpation.

External carotid artery (ECA): Supplies the face, oral cavity, scalp, and neck structures. It gives off eight major branches, typically described in anatomical order from inferior to superior, though variations are common.

The Eight Branches of the External Carotid Artery

Mnemonic: "Some Attendings Like Freaking Out Potential Medical Students" — Superior thyroid, Ascending pharyngeal, Lingual, Facial, Occipital, Posterior auricular, Maxillary, Superficial temporal.

1. Superior thyroid artery: First branch, supplies the thyroid gland, larynx, and infrahyoid muscles. Gives off the superior laryngeal artery, which pierces the thyrohyoid membrane with the internal laryngeal nerve.

1. Ascending pharyngeal artery: Small branch ascending on the pharyngeal wall; supplies pharyngeal muscles, soft palate, and meninges.

1. Lingual artery: Arises near the greater horn of the hyoid bone. Supplies the tongue (deep lingual artery), suprahyoid muscles, sublingual gland, and floor of mouth. The deep lingual artery runs along the ventral surface of the tongue and can be visible clinically. Clinical significance: The lingual artery is vulnerable during surgical procedures in the floor of the mouth. Hemorrhage from the lingual artery can be life-threatening due to its proximity to the airway.

1. Facial artery: Arises above the lingual artery. Has a tortuous course to accommodate mandibular movement — passes deep to the submandibular gland, crosses the inferior border of the mandible at the anterior border of the masseter (where the facial pulse can be palpated), and ascends across the face toward the medial canthus of the eye as the angular artery (terminal branch). Branches include:
   • Ascending palatine artery (soft palate, tonsil)
   • Submental artery (submandibular region and chin)
   • Inferior and superior labial arteries (lips)
   • Lateral nasal artery

1. Occipital artery: Posterior branch supplying the scalp and sternocleidomastoid muscle.

1. Posterior auricular artery: Supplies the auricle, scalp behind the ear, and part of the parotid gland. Gives off the stylomastoid artery, which enters the stylomastoid foramen to supply the facial nerve.

1. Maxillary artery (internal maxillary artery): THE most important artery for dental professionals. It is the larger of the two terminal branches of the ECA (the other being the superficial temporal artery). It supplies the deep structures of the face, including the jaws, teeth, muscles of mastication, TMJ, palate, nasal cavity, and meninges.

1. Superficial temporal artery: The smaller terminal branch. Ascends anterior to the ear, where its pulse is palpable. Supplies the scalp (frontal and parietal branches), parotid gland, and TMJ. Gives off the transverse facial artery.

The Maxillary Artery: The Dentist's Artery

The maxillary artery is divided into three parts based on its relationship to the lateral pterygoid muscle:

First part (mandibular portion): Proximal to (or medial to) the lateral pterygoid muscle. Branches:

• Inferior alveolar artery: Enters the mandibular foramen with the IAN. Within the mandibular canal, it gives off dental branches to the mandibular teeth, periodontal branches, and the mental artery (exiting the mental foramen). This is THE artery supplying the mandibular teeth.
• Deep auricular artery
• Anterior tympanic artery
• Middle meningeal artery: Ascends through the foramen spinosum to supply the dura mater and skull bones. It is the most clinically significant meningeal vessel — the anterior branch runs beneath the pterion (junction of frontal, parietal, temporal, and sphenoid bones). Fractures in this area can lacerate the middle meningeal artery, causing an epidural hematoma — a neurosurgical emergency.

• Accessory meningeal artery

Second part (pterygoid portion): Related to (usually lateral to or within) the lateral pterygoid muscle. Branches supply the muscles of mastication:

• Deep temporal arteries (anterior and posterior)
• Pterygoid branches
• Masseteric artery
• Buccal artery (supplies the buccinator muscle and buccal mucosa)

Third part (pterygopalatine portion): Distal to the lateral pterygoid muscle, within the pterygopalatine fossa. Branches:

• Posterior superior alveolar (PSA) artery: Enters the posterior superior alveolar foramina on the maxillary tuberosity. Supplies maxillary molars and premolars, buccal gingiva, and the maxillary sinus lining.
• Infraorbital artery: Passes through the inferior orbital fissure into the infraorbital canal, where it gives off the middle superior alveolar and anterior superior alveolar arteries. Exits the infraorbital foramen to supply the lower eyelid, side of nose, and upper lip.
• Greater (descending) palatine artery: Descends through the greater palatine canal and emerges at the greater palatine foramen to supply the hard palate and palatal gingiva. Gives off the lesser palatine artery to the soft palate.
• Sphenopalatine artery: The terminal branch. Enters the nasal cavity through the sphenopalatine foramen. Its terminal branch — the nasopalatine artery — descends through the incisive canal to anastomose with the greater palatine artery at the incisive papilla. Supplies the anterior palatal gingiva and the nasal septum. This is the artery responsible for significant bleeding during nasopalatine nerve block injections.

Dental Arterial Supply Summary

Venous Drainage and the Danger Zone

The venous drainage of the face and oral cavity is highly relevant to dental practice due to the risk of infection spread.

Facial vein (anterior facial vein): Drains the face and communicates with the superior ophthalmic vein at the medial canthus. The superior ophthalmic vein drains into the cavernous sinus.

Danger zone of the face (danger triangle): The area from the corners of the mouth to the bridge of the nose. Infections in this area (e.g., from a furuncle, or from an odontogenic infection tracking through venous channels) can spread RETROGRADE through the facial vein and superior ophthalmic vein to the cavernous sinus because these veins are VALVELESS. Cavernous sinus thrombosis is a life-threatening condition presenting with fever, periorbital edema, proptosis, chemosis, and cranial nerve palsies (CN III, IV, V1, V2, and VI pass through the cavernous sinus).

Pterygoid plexus of veins: A network of veins in the infratemporal fossa surrounding the lateral pterygoid muscle. It receives drainage from the maxillary veins and communicates with the facial vein, cavernous sinus, and inferior ophthalmic vein. The pterygoid plexus is a potential route for infection spread from odontogenic sources to the cavernous sinus. It is also at risk during PSA nerve block injections and maxillary tuberosity procedures.

Retromandibular vein (posterior facial vein): Formed by the union of the superficial temporal and maxillary veins within the parotid gland. It divides into anterior and posterior divisions: the anterior division joins the facial vein to form the common facial vein (draining into the internal jugular vein), and the posterior division joins the posterior auricular vein to form the external jugular vein.

Internal jugular vein: The major vein of the head and neck, receiving drainage from the brain, face, and neck. It descends within the carotid sheath and joins the subclavian vein to form the brachiocephalic vein.

Clinical Relevance for Dental Practice

Local anesthesia: Understanding arterial anatomy helps avoid intravascular injection. The PSA artery is near the PSA injection site. The inferior alveolar artery enters the mandibular foramen with the IAN — aspiration before injection is critical to prevent intravascular administration. The nasopalatine artery at the incisive papilla makes the nasopalatine injection one of the most painful and hemorrhagic.

Hemorrhage control: The facial artery at the inferior border of the mandible and the lingual artery in the floor of the mouth are important pressure points. The superficial temporal artery anterior to the tragus of the ear and the facial artery at the mandibular notch (antegonial notch) are sites where arterial pulses can be palpated.

Infection spread: Odontogenic infections can spread through facial spaces that are bounded by muscles and fascial planes. Ludwig's angina (bilateral cellulitis of the submandibular, sublingual, and submental spaces) can compromise the airway and requires emergent management. Infections can track to the mediastinum through the retropharyngeal space, or to the cavernous sinus through the valveless facial veins.

Common Traps

• Confusing the internal carotid artery (no branches in neck, supplies brain) with external carotid (multiple branches in neck, supplies face/jaws)
• Thinking the maxillary artery is a branch of the internal carotid — it's from the external carotid
• Forgetting that the venous system of the face is valveless — this is why infections can spread to the cavernous sinus
• Confusing the nasopalatine artery (at incisive papilla) with the greater palatine artery (at greater palatine foramen)
• Thinking the lingual artery is not clinically significant — floor-of-mouth hemorrhage can rapidly compromise the airway