The collateral ganglia are the synapse sites between the preganglionic and postganglionic fibers that innervate the abdominal and pelvic region organs.
The ganglia include the celiac, mesenteric, aorticorenal, and renal ganglia.
Preganglionic fibers enter the collateral ganglia as various splanchnic nerves and synapse with postganglionic fibers, innervating their targets.
The greater splanchnic nerve extends to the celiac ganglion and regulates structures in the stomach, spleen, pancreas, and gallbladder.
The lesser splanchnic nerve enters the aorticorenal and superior mesenteric ganglion, controlling the small intestine, colon, and kidney function.
The least splanchnic nerve extends to the renal plexus, regulating kidney function.
The lumbar and sacral splanchnic nerves travel to the inferior mesenteric ganglion and the hypogastric plexus, which supply sympathetic signals to the large intestine, urinary bladder, uterus, and genitals.
Some preganglionic fibers pass through the collateral ganglia without synapsing.
They enter the adrenal medulla and stimulate its chromaffin cells to release hormones such as epinephrine and norepinephrine in the bloodstream.
As a result, the adrenal medulla can regulate the activity of distant organs.