Anatomy: relations, nerve lesions and the spaces that matter
The Anatomy section of the UHS DES entrance examination rewards spatial reasoning rather than list recall. Questions cluster around structures whose relations matter at the bedside and in theatre: contents and boundaries of named spaces, the course of nerves and vessels against bone, and the deficit produced when a nerve is divided. Expect regional anatomy of head and neck, thorax, abdomen, pelvis and limbs, with a dependable minority of embryology and histology items.
What you must be able to state cold
- Contents of the femoral triangle, carpal tunnel and epiploic foramen, and the boundaries of the inguinal canal.
- Nerve lesion to deficit mapping: median nerve at the wrist (thenar wasting, loss of opposition, sensory loss over the lateral three and a half digits) versus at the elbow (hand of benediction).
- Cross-sectional relations: the three crossings of the ureter, structures passing through the diaphragm at T8/T10/T12, and the arterial supply of the internal capsule.
- Embryology: pharyngeal arch nerve and muscle derivatives, midgut rotation, and the branchial origin of lateral neck cysts.
Worked example
A newborn holds the right arm adducted, internally rotated and pronated, but moves the fingers normally. Reason it out: this is the waiter's tip posture of Erb's palsy. C5-C6 fibres run in the upper trunk of the brachial plexus, stretched by shoulder dystocia. The paralysed muscles are those of the axillary nerve (deltoid), suprascapular nerve (supraspinatus) and musculocutaneous nerve (biceps, brachialis). Hand function survives because C8-T1 fibres in the lower trunk are spared. The answer is therefore an upper trunk lesion, not a radial nerve palsy, which drops the wrist and spares the shoulder.
Traps that cost marks
- Radial nerve in the spiral groove spares the triceps but loses wrist extension; axillary nerve injury loses deltoid and a small badge of skin over the shoulder.
- Dermatomes overlap heavily; a single dermatome is not a single nerve.
- The ilioinguinal nerve runs in the inguinal canal but not through the deep ring.
- Right and left relations in the mediastinum and medulla are commonly reversed in the distractors.