Positioned in the middle of the low back, the L3-L4 spinal segment is susceptible to disc herniation, Lumbar Spine Anatomy Vertebrae L1 through L5 Watch: .4. 4000. 48 filters of stride 2. 160 filters of stride 2. 512 filters of stride 1. 6. 1200. L1. L2. L3. L4. L5 free space unknown observed surface observed points.