Head and Neck Anatomy
What this domain tests
Head and neck anatomy items test spatial relationships, cranial nerve branches, vasculature, fascial spaces, lymphatic drainage, and surface landmarks used for local anesthesia and surgery. The exam favors clinically consequential relationships over isolated names.
Core rules and concepts
- The trigeminal nerve has three divisions: V1 ophthalmic, V2 maxillary, and V3 mandibular. V3 supplies motor fibers to the muscles of mastication, mylohyoid, anterior digastric, tensor veli palatini, and tensor tympani.
- The facial nerve supplies muscles of facial expression. Chorda tympani carries taste from the anterior two-thirds of the tongue and parasympathetic fibers to the submandibular and sublingual glands.
- A lower motor neuron facial palsy affects the entire ipsilateral face, including the forehead. An upper motor neuron lesion spares the forehead because bilateral cortical input supplies the upper face.
- The lingual nerve lies close to the lingual plate in the third molar region and is at risk during retraction, flap elevation, or lingual plate fracture.
- The inferior alveolar nerve enters the mandibular foramen and terminates as the mental nerve at the mental foramen. The long buccal nerve is a sensory branch of V3, not a branch of the facial nerve.
- The danger space extends from the neck to the mediastinum, so deep neck infections can become life-threatening.
- Lymph node levels: level I submental and submandibular, level II upper jugular, level III mid-jugular, level IV lower jugular, and level V posterior triangle.
Worked example
After mandibular third molar removal, a patient reports altered tongue sensation and taste on the same side. The reasoning is that the lingual nerve carries general sensation to the anterior tongue and is joined by chorda tympani, so injury can affect both sensation and taste. Document the deficit, test light touch and taste, and arrange review; most injuries are neuropraxic and improve, but severe or persistent deficits need specialist assessment.
Traps that cost marks
Do not confuse the long buccal nerve with the buccal branch of the facial nerve. The facial nerve is motor to the face, not sensory. The mental nerve is a terminal branch of the inferior alveolar nerve. Also remember that the danger space communicates with the mediastinum, which changes the urgency of deep infections.