Pelvic splanchnic nerves
The pelvic splanchnic nerves (also called nervi erigentes) are the presynaptic parasympathetic nerve fibers that arise from the spinal roots S2, S3, and S4. These nerve fibers first travel within the anterior (ventral) rami of corresponding sacral spinal nerves (S2-S4). They then leave the nerves and freely distribute across the abdominal and pelvic cavities to innervate the abdominopelvic viscera.
The main function of the pelvic splanchnic nerves is to provide the parasympathetic input to the autonomic ganglia of the pelvis. This way, the pelvic splanchnic nerves provide parasympathetic innervation for the majority of the pelvic organs, including the urinary bladder, hindgut, ureter, prostate, urethra, and penis/clitoris.
This article will discuss the anatomy and function of the pelvic splanchnic nerves.
|Origin||Sacral spinal nerves (S2, S3, S4)|
|Supply||Parasympathetic innervation of bladder, descending colon, sigmoid colon, rectum, ureter, prostate, urethra and penis/clitoris|
Origin and course
The pelvic splanchnic nerves arise from the same nerves that participate in the formation of the sacral plexus. More specifically, their fibers originate in the spinal roots S2-S4 and run in the anterior/ventral rami of corresponding spinal nerves until they reach the anterior sacral foramina. Here, the fibers leave the spinal nerves, enter the presacral area and branch out into three main locations:
- The majority of the splanchnic fibers join the inferior hypogastric plexus, while the smaller portion of the fibers joins the hypogastric nerves and travels with them to the superior hypogastric plexus.
- The smallest portion of the pelvic splanchnic fibers runs across the pelvic brim to the retroperitoneal space to innervate the mesentery of the sigmoid and descending colon.
From the plexuses, the postganglionic fibers are distributed to the organs by traveling with the arteries as part of their periarterial nervous plexuses (e.g. periarterial plexuses of the branches of the inferior mesenteric artery). Upon reaching the organs, the pelvic splanchnic nerves supply the parasympathetic ganglions that are embedded in the walls of each organ.
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The principal function of the pelvic splanchnic nerves is to provide the presynaptic (preganglionic) parasympathetic nervous fibers to supply the abdominal and pelvic viscera. These nerves are in charge of the parasympathetic innervation of the urinary bladder, hindgut (descending colon, sigmoid colon, rectum), ureter, prostate, urethra, penis and clitoris.
More specifically, the activation of parasympathetic fibers in the pelvic splanchnic nerves leads to vasodilation of the erectile tissues in the penis and clitoris, secretion in the hindgut, and motor activity in the hindgut and urinary bladder.
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