Lumbar Plexus V2 Practice Test

The key idea is which nerves originate from the lumbar plexus versus from the sacral plexus. The lumbar plexus (L1–L4, sometimes with T12) sends out seven principal branches: iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, obturator, and the lumbosacral trunk. The sciatic nerve, on the other hand, comes from the sacral plexus (L4–S3) and travels to supply the posterior thigh and lower leg via its branches. So, the nerve not belonging to the lumbar-plexus set is the sciatic nerve, since it originates from the sacral plexus rather than the lumbar plexus. The other nerves listed are classic lumbar-plexus branches.