Autonomic plexuses of the abdomen and pelvis

In the abdominal cavity and in the pelvic cavity there are various sized vegetative nerve plexuses, consisting of vegetative nodes and bundles of nerve fibers connecting them. In the vegetative nodes there are bodies of neurons of the efferent path, the processes of which (postganglionic fibers) are directed from these plexuses to the internal organs and vessels for their innervation.

One of the largest vegetative plexuses of the abdominal cavity is the abdominal aortic plexus, located on the aorta and continuing on its branches.

The largest and most important part of the abdominal aortic plexus is the celiac plexus (plexus coeliacus), or, as it is also called, the "solar plexus" or "abdominal brain". The celiac plexus is located on the anterior surface of the abdominal aorta around the celiac trunk. It consists of several large nodes (usually five) and numerous nerves connecting these nodes. The celiac plexus includes two crescent-shaped celiac nodes located to the right and left of the celiac trunk. The left celiac node is adjacent to the aorta, the right - to the lower surface of the liver, in front - to the head of the pancreas. The celiac plexus includes two aortorenal nodes, each of which is located at the site of departure from the aorta of the corresponding renal artery, as well as an unpaired superior mesenteric node, located at the beginning of the artery of the same name. The right and left large and small thoracic visceral nerves, lumbar visceral nerves from the lumbar nodes of the sympathetic trunk approach the celiac plexus. The fibers of the posterior trunk of the vagus nerve, as well as the sensory fibers of the right phrenic nerve approach the celiac plexus but pass through its nodes in transit. Nerves that contain postganglionic sympathetic nerve fibers and preganglionic parasympathetic fibers from the branches of the vagus nerve, which independently or together with the vessels are directed to the organs, branch off from the nodes of the celiac plexus. Located around the vessels, the nerves form the so-called perivascular (periarterial) vegetative plexuses, and in the thickness of the internal organs - intraorgan vegetative plexuses.

Numerous vegetative (sympathetic) fibers run along the celiac trunk and its branches, forming plexuses of the same name around the common hepatic, splenic, left gastric arteries and their branches. Organ plexuses of parenchymatous organs are located not only around blood vessels, but also in the connective tissue stroma of organs. As a result, the gastric plexus (plexus gastrici), splenic plexus (plexus lienalis), hepatic plexus (plexus hepaticus), pancreatic-duodenal plexus (plexus pancreaticus), etc. are formed.

The nerve plexuses of the hollow internal organs: the stomach, small and large intestines, as well as the urinary and gall bladders, etc., are located between the layers of the organ walls. Thus, there are subserous, intermuscular and submucous plexuses that innervate the muscles of the organ walls and glands. From each celiac ganglion, branches extend to the adrenal glands, forming a paired adrenal plexus (plexus suprarenalis). The adrenal autonomic branches contain preganglionic sympathetic fibers that innervate the adrenal medulla. Thus, the adrenal medulla, which has a common origin with the nodes of the autonomic nervous system, unlike any other organs, receives innervation directly due to preganglionic sympathetic nerve fibers that end in effector nerve endings on the secretory cells of the medulla.

The abdominal aortic plexus (plexus aorticus abdominalis) is a direct continuation of the celiac plexus. This plexus is a plate of nerve fibers and nodes located on the anterior surface of the aorta from the celiac trunk to the superior mesenteric artery, and even to the inferior mesenteric artery. At the level between the two mesenteric arteries, this plexus is called the intermesenteric plexus (plexus intermesentericus).

The abdominal aortic plexus gives off thin branches to the renal vessels, in the adventitia of which the paired renal plexus (plexus renalis) is formed. The formation of the renal plexus involves branches of the superior nodes of the lumbar sympathetic trunk, as well as preganglionic parasympathetic fibers from the branches of the right vagus nerve. In the renal plexus, one or two fairly large renal nodes (ganglia renalia) and a large number of small nodes are constantly encountered. Large renal nodes are located in front of and below the renal artery. Sympathetic fibers of the renal plexus penetrate the kidney along the branches of the artery of the same name and also pass to the ureter, participating in the formation of the ureteral plexus (plexus uretericus).

The branches of the abdominal aortic plexus accompany the blood vessels of the sex glands. In men, the paired testicular plexus (plexus testicularis) is located along the testicular arteries. In women, the paired ovarian plexus (plexus ovaricus) also descends into the small pelvis along the ovarian arteries.

The branches of the superior mesenteric node, as well as the abdominal aortic plexus, pass to the superior mesenteric artery, forming the superior mesenteric plexus.

The superior mesenteric plexus (plexus mesentericus superior) is located at the base of the superior mesenteric artery, at the level of the first lumbar vertebra, and also in the adventitia of this large blood vessel. This plexus continues to the intestinal and colonic arteries, reaching the small, blind, ascending and transverse colons, in the walls of which there are subserous, muscular-intestinal and submucous plexuses.

The continuation of the abdominal aortic plexus is the inferior mesenteric plexus (plexus mesentericus inferior). Branches from the superior lumbar nodes of the sympathetic trunk also enter this plexus. Along the branches of the inferior mesenteric artery, the nerves of this plexus reach the sigmoid, descending and left half of the transverse colon and form the subserous, muscular-intestinal and submucous plexuses in their walls. The superior rectal plexus (plexus rectalis superior), which accompanies the artery of the same name, originates from the inferior mesenteric plexus.

The abdominal aortic plexus continues onto the common iliac arteries in the form of the right and left iliac plexuses (plexus iliaci), and also gives off several fairly large nerves that pass into the superior hypogastric plexus (plexus hypogastricus superior. This plexus is located on the anterior surface of the aorta and below its bifurcation, on the bodies of the lower lumbar vertebrae and on the sacrum. The superior hypogastric plexus consists of flat bundles of nerve fibers. This plexus also receives visceral nerves from the lower lumbar and three upper sacral nodes of the right and left sympathetic trunks.

A little below the sacral promontory, the superior hypogastric plexus divides into two bundles - the right and left hypogastric nerves, united by the name "pelvic plexus". Behind the peritoneum, the hypogastric nerves descend into the cavity of the small pelvis and form a paired inferior hypogastric plexus.

The inferior hypogastric plexus (plexus mesentericus inferior) consists of bundles of vegetative fibers descending into the small pelvis from the superior hypogastric plexus, as well as branches from the nodes of the sacral section of the sympathetic trunks and fibers of the pelvic (parasympathetic) visceral nerves. The right and left inferior hypogastric plexuses are located on the posterior wall of the small pelvis. The medial part of each inferior hypogastric plexus in men is adjacent to the lateral surface of the ampulla of the rectum, and reaches the seminal vesicle in front. The plexus continues onto the urinary bladder and prostate gland in the form of the vesical plexus (plexus vesicalis), prostatic plexus (plexus prostaticus), plexus of the vas deferens (plexus deferentialis) and other organ plexuses. In women, the inferior hypogastric plexus is also located on the sides of the rectum, in front it reaches the cervix and the vaginal vault - it forms the uterovaginal plexus and passes to the urinary bladder. The lateral edge of the inferior hypogastric plexus reaches the large vessels of the small pelvis.

The nodes of the inferior hypogastric plexus have different sizes and shapes. In addition to the nodes, there are many individual neurons in the nerve bundles.