Sacral ganglia

The sacral ganglia are a group of four ganglia situated along the inferior sacral (or pelvic) ends of the sympathetic trunks and are interconnected with each other via interganglionic fibers within the sympathetic chains. These sacral sympathetic chains descend on the anterior surface of the sacrum, medial to the anterior sacral foramina. They eventually fuse together with each other in the midline–in front of the coccyx–to form the ganglion impar.

The sacral ganglia give off the following branches:

• Gray rami communicantes, which connect the sacral ganglia with the sacral spinal nerves. These convey post-ganglionic sympathetic neurons from the ganglia to the ventral rami of sacral spinal nerves.

• Sacral splanchnic nerves, which run medially towards the inferior hypogastric or pelvic plexus. These contain preganglionic sympathetic neurons that synapse with the ganglia within the pelvic plexus. From here onwards, post-ganglionic neurons reach out to various pelvic viscera and end up providing sympathetic innervation to them.

Please note that the parasympathetic innervation to pelvic viscera arises via the pelvic splanchnic nerves. Both sacral and pelvic splanchnic nerves also contain visceral afferent neurons that transmit sensory information from the pelvic viscera to the central nervous system.