Anatomy: Applied Topography and Clinical Correlates
Anatomy in a primary emergency examination is applied anatomy: the question usually describes a lesion and asks which structure is injured or which deficit appears. Build your knowledge around topographical relationships rather than isolated lists. For the upper limb, understand the brachial plexus as cords and terminal branches with the axillary artery as the central landmark, so that a proximal humeral fracture threatens the axillary nerve (deltoid weakness, regimental badge sensory loss) and a mid-shaft humeral fracture threatens the radial nerve (wrist drop). For the lower limb, know the femoral triangle contents from lateral to medial, and why the femoral nerve, artery and vein are at risk in penetrating groin trauma.
In the thorax, distinguish structures that are vulnerable by their surface relations: the intercostal neurovascular bundle runs in the costal groove, so chest drains are placed above the rib below. In the abdomen, know the peritoneal attachments that determine where free fluid collects, and the retroperitoneal organs that may bleed without peritonism.
Traps include confusing sensory dermatomes with peripheral nerve territories, and forgetting that a nerve injury may be masked by a fracture or by swelling.
Rule of thumb
When a stem describes a fracture with a specific neurological deficit, name the nerve by its relationship to the bone, not by the muscle alone. For example, a humeral shaft fracture with inability to extend the wrist points to the radial nerve in the spiral groove; the same deficit after axillary crutch use points instead to pressure in the axilla. Location plus mechanism localises the lesion.