1.3 Vascular Supply, Lymphatics, TMJ & Mastication

Quick Answer: Trace external carotid → maxillary/facial/lingual arteries for oral bleeding and blocks; remember pterygoid plexus → cavernous sinus venous risk; map submental/submandibular → deep cervical lymph nodes; and know TMJ disc + V3-innervated muscles of mastication for movement and trismus questions.

This section closes head-and-neck anatomy for the AFK biomedical domain by integrating vessels, nodes, the temporomandibular joint, and the muscles that move it.

Arterial Supply of the Oral and Maxillofacial Region

The common carotid bifurcates into internal (no cervical branches to the face) and external carotid arteries. Nearly all dental and facial soft-tissue supply is external carotid.

Major External Carotid Branches (Dental Focus)

The maxillary artery arises behind the neck of the condyle in the parotid region, courses through the infratemporal fossa (near lateral pterygoid), and enters the pterygopalatine fossa. Clinically important branches:

• Inferior alveolar artery: enters mandibular foramen with IAN; supplies mandibular teeth and bone; mental artery exits mental foramen. Severing the bundle in the canal causes pulsatile bleeding that is hard to control without packing/pressure/local measures.
• Middle meningeal: enters foramen spinosum—intracranial; mentioned because foramen spinosum is a sphenoid landmark, not because dentists ligate it.
• Posterior superior alveolar: maxillary molars and sinus walls.
• Infraorbital: midface and anterior maxillary teeth via superior alveolar branches.
• Descending palatine → greater/lesser palatine: hard and soft palate.
• Sphenopalatine: nasal cavity (epistaxis source).
• Buccal, deep temporal, masseteric, pterygoid branches: muscles of mastication and buccal region.

The facial artery crosses the inferior border of the mandible at the anterior border of masseter (pulse point) and courses toward the angle of the mouth and nose as the angular artery, anastomosing with the dorsal nasal/ophthalmic system—relevant to the danger triangle’s arterial as well as venous richness.

Venous Drainage and the Pterygoid Plexus

Veins of the face generally parallel arteries but have critical communications:

• Facial vein → internal jugular pathway; connects via angular/ophthalmic veins to cavernous sinus.
• Pterygoid venous plexus in the infratemporal fossa surrounds the maxillary artery and communicates with the cavernous sinus (via emissary veins through foramina such as ovale/lacerum region pathways), the facial vein (via deep facial vein), and inferior ophthalmic veins.

Needle trauma or infection in the pterygomandibular/infratemporal region can involve this plexus → hematoma after PSA or IAN injection, or septic spread toward the cavernous sinus. PSA injections that are too deep/posterior risk hematoma from the plexus.

Lymphatic Drainage of the Teeth and Oral Cavity

Lymphatic mapping matters for infection and malignancy staging questions.

Rule of thumb for AFK: lower incisors → submental first; most other teeth → submandibular first; both then pass to deep cervical chains along the internal jugular. Midline structures may drain bilaterally—important for cancer and bilateral node exam findings.

Temporomandibular Joint (TMJ)

The TMJ is a synovial, ginglymoarthrodial (hinge + sliding) joint between the mandibular condyle and the glenoid (mandibular) fossa / articular eminence of the temporal bone. A biconcave articular disc (fibrocartilage) divides the joint into superior and inferior compartments:

• Inferior compartment: primarily rotation (hinge) of condyle against disc in early mouth opening.
• Superior compartment: primarily translation (sliding) of disc-condyle complex down the articular eminence in wider opening.

Ligaments: temporomandibular (lateral) ligament limits posterior displacement; sphenomandibular and stylomandibular are accessory. The retrodiscal tissue (bilaminar zone) is vascular and innervated—pain source when the disc is anteriorly displaced and the condyle loads retrodiscal tissue.

Innervation of TMJ: chiefly auriculotemporal nerve (V3), with contributions from masseteric and deep temporal nerves. Blood supply: superficial temporal and maxillary branches.

Disc displacement with reduction classically produces a click as the condyle recaptures the disc; without reduction may limit opening (closed lock). AFK expects structural understanding more than full TMD management algorithms (those appear more in orofacial pain sections).

Muscles of Mastication

All four classical muscles are V3 motor:

Exam traps:

• Lateral pterygoid is the muscle most associated with protrusion and disc attachment—not masseter.
• Temporalis posterior fibers retract; they do not open the mouth.
• Opening against resistance also uses suprahyoid muscles (digastric, geniohyoid, mylohyoid) with hyoid stabilization by infrahyoids—these are not “muscles of mastication” in the classical four, but they matter functionally.
• Trismus after infection or injection into medial pterygoid/masseter reflects inflammation in the masticator space, not necessarily joint ankylosis.

Unilateral lateral pterygoid action moves the mandible to the opposite side (contralateral excursion). In deviation on opening, think which side is hyper-/hypoactive or which joint is not translating.

Accessory and Facial Muscles Touching Dentistry

• Buccinator (CN VII): keeps food on the occlusal table; pierced by the parotid duct (Stensen) opposite maxillary second molar (FDI 17/27 region).
• Mylohyoid (V3 via mylohyoid nerve): floor of mouth diaphragm—space divider discussed in §1.1.
• Genioglossus (XII): protrudes tongue; safety muscle preventing airway obstruction by tongue fall.
• Orbicularis oris (VII): lip competence for impressions and prostheses.

Integrated Clinical Scenarios

1. Hematoma after PSA block: overinsertion into pterygoid plexus / PSA vessels; swelling in buccal vestibule/cheek; manage with pressure, ice, reassurance; delay further surgery if needed.
2. Bleeding from mandibular implant osteotomy: inferior alveolar artery in canal or lingual sublingual/submental arterial injury if lingual cortex perforated—floor-of-mouth hematoma can threaten airway.
3. Nodes with a non-healing ulcer on the lower lip: submental ± submandibular drainage pathways before deep cervical.
4. Limited opening with preauricular pain and click history: TMJ disc mechanics; distinguish from masticator-space infection with fever and odontogenic source.
5. Deviation of jaw to the left on protrusion: right lateral pterygoid weakness (or left joint mechanical lock)—apply the contralateral excursion rule carefully to the stem.

Summary Table — AFK Vascular & TMJ Anchors

Together with osteology/spaces and cranial nerves, this triad lets you reason through anesthesia failures, infection pathways, bleeding emergencies, nodal spread, and jaw movement disorders on the AFK.