The inferior hypogastric plexus, the hub of all autonomic control within the pelvis, is a paired meshwork of nerves located on either side of the rectum lying medial to the internal iliac vessels. The sympathetic contributions into the inferior hypogastric plexuses stem from two sources. The largest sympathetic contribution is from the superior hypogastric plexus. The superior hypogastric plexus contains no parasympathetic fibers, so it is a purely sympathetic plexus. The superior hypogastric plexus itself receives upper lumbar contributions from the intermesenteric plexus, as well as contributions from L3 and L4 splanchnic nerves. Located within the abdomen at the bifurcation of the aorta, the superior hypogastric plexus descends into the pelvis and bifurcates as the right and left hypogastric nerves. Please note these "nerves" aren’t really what is traditionally thought of as a nerve, they are more like meshworks than solid nerve trunks. These nerve meshworks diverge lateral to the rectum on either side and curve outward and backward as they make their way down about 7.5 – 10 centimeters into the pelvis. They interconnect the superior and inferior hypogastric plexuses and contain no ganglia. The hypogastric nerves convey the majority of the sympathetic contribution from the superior hypogastric plexus into the inferior hypogastric plexuses.
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