Human abdomen. Coloured computed tomography (CT) scan of an axial section through the lower abdomen showing a healthy vertebra and the intestine. In this horizontal slice through the abdomen, the patient's back is at bottom frame. At centre (yellow) is a lumbar vertebra of the lower spine with its spinal process pointing downwards. The spine protects the spinal cord (purple triangle). On either side of the vertebra are rounded psoas major muscles (purple) with erector spinae muscles of the back below the vertebra. Above the spine are major blood vessels (red). Much of the rest of the abdomen contains the intestine (yellow).