Prevertebral Ganglia And Plexus

The prevertebral (preaortic) plexus is a network of autonomic nerve fibers covering the abdominal aorta and extending into the pelvic cavity between the common iliac arteries. This plexus serves as a common pathway for the following autonomics (Figure 11-4A and B):

Preganglionic sympathetic nerves. From greater, lesser, least, and lumbar splanchnic nerves.

Preganglionic parasympathetic nerves. From the vagus nerve (CN X) and pelvic splanchnics (S2-S4). Visceral afferents. From both sympathetic and parasympa-thetic pathways.

Sympathetic (prevertebral) ganglia that are named for the associated branch of the abdominal aorta are located within the prevertebral plexus. These ganglia are collections of postgan-glionic sympathetic neurons. Neurons within the prevertebral plexus connect autonomics to and from the digestive, urinary, and reproductive organs.

The prevertebral plexus is subdivided into smaller plexuses and ganglia. Many of these plexuses and ganglia are located very close together and are variable and interrelated. Their principal features can be described as follows:

Celiac ganglia and plexus. Located around the origin of the celiac trunk and distributed along its branches. The celiac plexus receives preganglionic sympathetic nerves from the greater splanchnic nerve. Parasympathetics from the vagus nerve course through the celiac ganglion en route to the viscera without synapsing. Nerves exiting the celiac ganglion supply postganglionic sympathetic nerves to the liver, gallbladder, stomach, spleen, pancreas, and proximal part of the duodenum.

Superior mesenteric ganglia and plexus. Located around the origin of the superior mesenteric artery and distributed along its branches. The ganglia receive preganglionic contributions from the lesser splanchnic nerve. The superior mesen-teric plexus supplies postganglionic sympathetic fibers to the head of the pancreas; the distal part of the duodenum; the jejunum, ileum, and cecum; the ascending colon; and the transverse colon.

Aorticorenal ganglia and plexus. Located at the origin of the renal arteries and distributed along their branches. The ganglia receive contributions from the lesser splanchnic nerves and supply the adrenal glands, the kidneys, and the proximal part of the ureters.

Inferior mesenteric ganglia and plexus. Located at the origin of the inferior mesenteric artery and distributed along its branches. The inferior mesenteric ganglion receives contributions from the superior mesenteric plexus, the first and second lumbar splanchnic nerves (sympathetics), and fibers from the superior hypogastric plexus (sympathetics and parasympathetics). The inferior mesenteric plexus supplies the descending colon, the sigmoid colon, and the upper portion of the rectum.

Superior hypogastric plexus. Located inferior to the bifurcation of the aorta, between the common iliac arteries. The superior hypogastric plexus is formed by contributions of the inferior mesenteric plexus, the third and fourth lumbar splanchnic nerves (sympathetics), and the parasympathetic nerves that ascend from the inferior hypogastric plexus. The superior hypogastric plexus continues caudally into the pelvis via the hypogastric nerves.

Inferior hypogastric plexus and pelvic ganglia. In males, the inferior hypogastric plexus is posterolateral to the bladder, seminal vesicles, and prostate. In females, it is posterolateral to the bladder and cervix. The inferior hypogastric plexus and pelvic ganglia are formed primarily from the following fibers:

• Sympathetics. Preganglionic sympathetic fibers enter the inferior hypogastric plexus through the sacral splanchnic nerves. Additionally, some sympathetic fibers arising from the lumbar splanchnic nerves descend from the superior hypogastric plexus into the inferior hypogastric plexus. Preganglionic sympathetic neurons usually synapse with postganglionic sympathetic neurons somewhere in the prevertebral plexus (i.e. inferior hypogastric plexus).

• Parasympathetics. Preganglionic parasympathetic fibers enter the inferior hypogastric plexus through the pelvic splanchnic nerves. Once most of the parasympathetic fibers enter the inferior hypogastric plexus, they ascend out of the pelvis and into the superior hypogastric plexus to innervate the hindgut. However, some nerves exit the pelvis to innervate the urinary and reproductive systems. Preganglionic parasympathetic neurons usually synapse with postganglionic parasympathetic neurons somewhere in the wall of the target organ (i.e., Aurbachis plexus).

Parasympathetic

Anterior vagal trunk Posterior vagal trunk

Prevertebral ganglia and plexus on the aorta

Celiac ganglion, plexus, and trunk

- Superior mesenteric ganglion, plexus, and trunk

- Inferior mesenteric ganglion, plexus, and trunk

Superior hypogastric plexus - Hypogastric nn.

Inferior hypogastric plexus

Sympathetic

Sacral splanchnic nn.

Sympathetic

Prevertebral ganglia and plexus on the aorta

Celiac ganglion, plexus, and trunk

Superior Mesenteric Ganglia

Rami communicantes

Sympathetic

Lumbar splanchnic nn.

Sympathetic trunk and ganglion

Parasympathetic

Pelvic splanchnic nn.

Rectum

Figure 11-4: (continued) B. Anterolateral view of the autonomics of the posterior abdominal wall.

Sympathetic

Greater, lesser and least splanchnic nn.

Rami communicantes

Sympathetic

Lumbar splanchnic nn.

Sympathetic trunk and ganglion

Parasympathetic

Pelvic splanchnic nn.

Rectum

Figure 11-4: (continued) B. Anterolateral view of the autonomics of the posterior abdominal wall.

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