Parasympathetic pelvic splanchnic nerves

Last revised by Craig Hacking on 19 Oct 2022

The pelvic splanchnic nerves, also known as nervi erigentes, are preganglionic (presynaptic) parasympathetic nerve fibers that arise from the S2, S3 and S4 nerve roots of the sacral plexus. These nerves form the parasympathetic portion of the autonomic nervous system in the pelvis.  

The pelvic splanchnic nerves are preganglionic nerves that arise from the lateral horn grey matter of the spinal cord at the sacral segments of the S2, S3 and S4. The greatest contribution of these fibers is usually from the S3 nerve. 

The pelvic splanchnic nerves join with one another and ascend to join the ipsilateral inferior hypogastric plexus. The inferior hypogastric plexuses are paired structures that lie on either side of the rectum and contain both sympathetic and parasympathetic fibers. After reaching the inferior hypogastric plexus, the pelvic splanchnic nerves ramify throughout the pelvis and lower abdomen innervating ganglia embedded in walls of the descending and sigmoid colon, rectum, ureter, prostate, bladder, urethra and penis.

It should be noted that on the left some fibers rise out of the pelvis, pass to the left of the superior hypogastric plexus and join the periarterial inferior mesenteric plexus to supply the large intestine distal to the splenic flexure.

The pelvic splanchnic nerves and the hypogastric plexuses merge within the pelvis. The superior hypogastric plexus is a continuation of the intermesenteric plexus which sits just inferior to the bifurcation of the aorta. The superior hypogastric plexus enters the pelvis dividing into right and left hypogastric nerves which descend on the anterior surface of the sacrum to the lateral aspect of the rectum within ‘hypogastric sheaths’ and merge with the pelvic splanchnic nerves to form left and right inferior hypogastric plexuses.

The pelvic splanchnic nerves have a variable course of joining with one another until they merge with the hypogastric nerves on either side of the rectum.

The term 'splanchnic' is derived from the Greek word σπλαγχνον (splanchnon) meaning 'the innards' 5,6.

Hirschsprung disease (also known as aganglionic megacolon) is the congenital absence of parasympathetic ganglia within the large bowel. The resulting lack of peristalsis in the affected bowel segment causes obstruction and enlargement of the bowel proximal to the aganglionic segment. The incidence of Hirschprung disease is approximately 1 in 5000 live births and treatment is resection and removal of the aganglionic portion of bowel. 

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Cases and figures

  • Figure 1: sacral plexus
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