Pelvic splanchnic nerves represent the sacral part of parasympathetic nervous system in pelvis. They contain the preganglionic parasympathetic fibers as well as the visceral afferent fibers. The pelvic splanchnic nerves should not be confused with the sacral splanchnic nerves, which represent the sympathetic part of autonomic nervous system and arise from the sympathetic trunk.
Origin and Distribution:
The pelvic splanchnic nerves arise from the 2nd, 3rd and 4th sacral spinal nerves. After their origin, they travel to the corresponding inferior hypogastric plexus located on the wall of the rectum. The preganglionic parasympathetic fibers may synapse in ganglia of inferior hypogastric plexus or they may continue to the walls of viscera.
Some of the parasympathetic fibers ascend through the hypogastric plexus, and reach the inferior mesenteric plexus via the aortic plexus. These parasympathetic fibers are then distributed along the branches of the inferior mesenteric artery to supply the large intestine from left colic flexure to the upper half of the anal canal.