Applied Anatomy for the Anesthesia Candidate
What you must own
Applied anatomy questions test whether you can translate a surface landmark or a needle path into a structure at risk. Prioritise: the airway (mouth opening, temporomandibular joint, tongue base, vallecula, aryepiglottic folds, vocal cords, cricothyroid membrane between thyroid and cricoid cartilage), the vertebral column and its ligamentous layers for neuraxial access (supraspinous, interspinous, ligamentum flavum, dura, arachnoid), the brachial plexus (interscalene, supraclavicular, infraclavicular, axillary approaches and their neighbours - phrenic nerve, pleura, subclavian vessels), the femoral triangle (nerve, artery, vein medial-to-lateral: NAVEL), and the epidural venous plexus and artery of Adamkiewicz for thoracic procedures.
Traps that recur
- Confusing the cricothyroid membrane level (between thyroid and cricoid cartilage) with the cricoid ring itself.
- Forgetting that the adult spinal cord ends around L1–L2, so safe lumbar puncture is at or below L3–L4 in adults (lower in infants).
- Mixing up the order of structures in the femoral triangle or the relationship of the internal jugular vein to the carotid (vein lateral, artery medial).
- Assuming the right internal jugular lies directly over the carotid - it is usually anterolateral.
Rule of thumb
Use the "one structure at a time" method: for any block or line, name the target, then the structure immediately medial, lateral, anterior and posterior to it. Most distractors are simply one of these four neighbours.
Worked example
Question asks which nerve is most at risk during interscalene block. The phrenic nerve runs on the anterior scalene, immediately anterior/medial to the plexus - so the answer is phrenic nerve, not the recurrent laryngeal or long thoracic.