Anatomy and Physiology (Head and Neck)
What this domain tests
Head and neck items reward three-dimensional recall: which nerve, which foramen, which fascial space, and which structure is at risk in a named procedure. Physiology questions cluster around calcium and bone homeostasis, salivary function and haemostasis as they apply to dental treatment.
Core anatomy
- Trigeminal divisions. V1 exits the superior orbital fissure, V2 the foramen rotundum, V3 the foramen ovale. V3 is motor to all four muscles of mastication (masseter, temporalis, medial and lateral pterygoid), plus mylohyoid, anterior digastric and tensor veli palatini. The lateral pterygoid opens and protrudes the mandible.
- Maxillary branches of clinical weight: middle and posterior superior alveolar, infraorbital, greater and lesser palatine, nasopalatine (enters the incisive canal), zygomatic.
- Mandibular nerve. The inferior alveolar nerve gives the mylohyoid nerve before entering the mandibular foramen and exits as the mental nerve at the mental foramen, usually below the second premolar apices. The lingual nerve lies anterior and medial to it and carries chorda tympani taste fibres for the anterior two-thirds of the tongue.
- Facial nerve. Temporal, zygomatic, buccal, marginal mandibular and cervical branches; the temporal and marginal mandibular branches are most exposed during TMJ and submandibular surgery.
- Arteries. The maxillary artery gives the middle meningeal, inferior alveolar, posterior superior alveolar, infraorbital, greater palatine and sphenopalatine arteries. The pterygoid venous plexus communicates with the cavernous sinus, explaining the hazard of posterior superior alveolar injections and of spreading odontogenic infection.
Physiology worth memorising
Parathyroid hormone raises serum calcium by mobilising bone, increasing renal reabsorption and activating vitamin D; calcitonin and phosphate oppose it. Salivary flow falls with anticholinergics, radiotherapy and Sjögren syndrome, and bicarbonate buffering and secretory IgA are lost with it.
Worked example
A patient reports lower lip and chin numbness after removal of a deeply impacted mandibular third molar. Which structure is injured, and why is the lingual nerve a separate risk? Reasoning: the inferior alveolar nerve runs in the mandibular canal, which may be corticated-deficient or lie lingually at the third molar; horizontal impaction and apically curved roots raise risk. The lingual nerve runs in lingual soft tissue, typically just below the alveolar crest lingual to the retromolar region, so lingual retraction and lingual bone removal injure it independently. A mylohyoid branch can also supply the first molar, explaining a failed inferior alveolar block.
Traps
Treating the buccal nerve as a branch of the lingual nerve; forgetting the mylohyoid nerve; misjudging the mental foramen level; attributing muscles of facial expression to V3.