The sympathetic trunk and the splanchnic nerves pass dorsal to the diaphragm as they enter the abdomen. The greater splanchnic nerves have already been traced to the celiac ganglion on either side as they emerge from behind the diaphragm. The sympathetic trunk lies on the lateral side of the vertebral bodies and is thus covered by the crura of the diaphragm as it enters the abdomen. Find the trunk and follow it from thorax to pelvis. Dissect the trunk carefully and locate examples of lumbar splanchnic nerves and communicating rami .
Splanchnic nerves enter the aortic plexus .
The Lumbar Plexus Clean the fascia from the quadratus lumborum , iliacus and psoas major muscles . Nerves will be seen emerging in the interval between the psoas and iliacus muscles. These are nerves of the lumbar plexus which are connected to the sympathetic trunk through the communicating rami just dissected. Nerves arising from this plexus vary in their formation and are associated with the psoas major muscle in a variable manner. Often there is a psoas minor muscle , the tendon of which can be seen on the anterior surface of the psoas major.