During surgical removal of a submandibular calculus, the surgeon must identify the relationship between the lingual nerve and the submandibular duct. At the level of the third molar, what is their arrangement?

• A The nerve runs parallel to the duct without crossing it
• B The nerve lies medial to the duct throughout its course
• C The nerve lies lateral to the duct and crosses below it to become medial near the anterior end ✓
• D The nerve lies superficial to the mylohyoid muscle throughout

Explanation

On hyoglossus, the lingual nerve starts lateral to the submandibular duct, hooks beneath it, and ascends medially to enter the tongue, producing a double crossing. This close spiral relationship at the third molar places the nerve at risk during duct exploration and third molar surgery. The nerve lies deep to mylohyoid on hyoglossus, so a purely superficial or non-crossing course describes neither structure correctly.

Reference: BD Chaurasia Human Anatomy, Head and Neck, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.