[Fig. 164].—Sympathetic and Vagus in the Abdomen (somewhat Schematic).
![[Fig. 164]](#3418956513767812439_illo407lg.jpg.id-3055369673938149481.wrap-0.html.html){kind=link}
1, stomach; 2, crus and cut edge of diaphragm; 3, aorta; 4, cœliac artery; 5, superior mesenteric artery; 6, kidney; 7, inferior mesenteric artery; 8, large intestine. a, main trunk of sympathetic; b, great splanchnic nerve; c, lesser splanchnic nerves; d, cœliac (or semilunar) ganglion; e, cœliac plexus; f, superior mesenteric ganglion; g, superior mesenteric plexus, following the artery; h, aortic plexus; i, inferior mesenteric ganglion and plexus; j, suprarenal plexus on suprarenal body; k, renal plexus following renal artery; l, ventral œsophageal branch of vagus, forming anterior gastric plexus; m, dorsal œsophageal branch of vagus, forming posterior gastric plexus.
The cœliac ganglion (d) receives from the sympathetic (a), in addition to the great splanchnic nerve, two (or three) lesser splanchnic nerves (c), which arise from the main trunk of the sympathetic, the first just as it reaches the abdominal cavity, the second one or two centimeters caudad of the diaphragm.
From the cœliac and superior mesenteric ganglia a network of nerves passes in all directions to the abdominal viscera. These nerves follow especially the arteries, forming plexuses over their surfaces, and passing with them to the organs which they supply. The cœliac plexus anastomoses with the posterior gastric plexus of the vagus. Parts of the cœliac plexus following the branches of the cœliac artery may be distinguished as hepatic plexus, splenic plexus, etc. A dense plexus is formed on the surface of the suprarenal body (suprarenal plexus, j), and a renal plexus (k) follows the renal artery to the kidneys (6). The superior mesenteric plexus (g) forms a dense network over the superior mesenteric artery (5) and follows it to the intestine. A plexus passes caudad on the aorta (aortic plexus, h). This is a continuation of the cœliac and superior mesenteric plexuses; it receives a number of branches from the main sympathetic trunk, lying dorsad of the aorta. The aortic plexus contains a number of small ganglia.
From the aortic plexus the smaller inferior mesenteric plexus (i) follows the inferior mesenteric artery (7) to the large intestine; in this lies a ganglion of considerable size, the inferior mesenteric ganglion.
In the pelvic region small plexuses are formed in a similar manner, from branches given off by the main sympathetic trunk, together with branches from the plexuses of the abdominal cavity. These plexuses supply the various organs in the pelvis.
The main sympathetic trunk (a) passes into the abdomen at the side of the crus of the diaphragm, lying dorsad of the great splanchnic nerve (b). In the abdomen it lies nearer the middle line than in the thorax, so that the two trunks of right and left side are separated by but a few millimeters as they lie on the ventral surface of the centra of the lumbar vertebræ. There is a ganglion for each vertebra ([Fig. 162], n), and from each ganglion are given off one or more communicating branches to the spinal nerves, and usually a branch which passes ventrad to join one of the plexuses among the viscera. The first three branches of this kind ([Fig. 164], c) are larger and pass to the cœliac and superior mesenteric ganglia. The sympathetic may be traced into the pelvis, where it becomes smaller, and is lost as the caudal region is reached.