170. Veins of the Vertebral Column: Vertebral Veins 171. Muscles of Back: Superficial Layers 172. Muscles of Back: Intermediate Layers 173. Muscles of Back: Deep Layers 174. Nerves of Back 175. Suboccipital Triangle 176. Lumbar Region of Back: Cross Section 177. Typical Thoracic Spinal Nerve: Cross Section