The =solar plexus= (Fig. 450) is situated on the dorsal wall of the
abdominal cavity in relation to the aorta and the origin of its chief
visceral branches. It comprises the cœliaco-mesenteric ganglia and the
cœliac and anterior mesenteric plexuses.
The =cœliaco-mesenteric ganglia=[212] are two in number, right and left.
They are situated on each side of the aorta, in relation to the origin
of the cœliac and anterior mesenteric arteries. The right ganglion is
concealed by the posterior vena cava; it is irregularly quadrilateral
and is about two inches (4 to 6 cm.) in length. The left ganglion is
largely covered by the left adrenal; it is narrower than the right one
and is three or four inches (ca. 8 to 10 cm.) long. The two ganglia are
united by irregular connecting branches in front of and behind the
anterior mesenteric artery.[213] Each receives the splanchnic nerve of
its own side and branches from the dorsal œsophageal continuation of the
vagus nerves. Branches from the ganglia and the cords which connect them
pass back to the small stellate =posterior mesenteric ganglia=, which
are situated at the origin of the posterior mesenteric artery.
The =cœliac plexus= (P. cœliacus) consists of a feltwork of nerve-fibers
in which are small ganglia. It surrounds the cœliac artery and from it
proceed the following unpaired secondary plexuses which accompany the
arterial branches:
1. The =gastric plexus= (P. gastricus) enlaces the gastric artery and
divides like the artery into two parts, forming the anterior and
posterior gastric plexuses. These receive branches of the vagus nerves.
2. The =hepatic plexus= (P. hepaticus) is formed by several nerves of
considerable size which accompany the hepatic artery and the portal
vein. It receives fibers from the left vagus, ramifies in the liver, and
gives off branches which accompany the collateral branches of the
hepatic artery and supply the areas in which these vessels are
distributed.
3. The =splenic plexus= (P. lienalis) resembles the preceding in its
arrangement. In addition to its terminal branches to the spleen, it
gives collateral twigs to the pancreas and the left part of the greater
curvature of the stomach.
The =anterior mesenteric plexus= (P. mesentericus cranialis) is formed
mainly by branches from the posterior part of the cœliaco-mesenteric
ganglia; it is continuous with the cœliac plexus in front and the
posterior mesenteric behind. It surrounds the anterior mesenteric trunk
and its branches, and supplies the viscera to which these vessels are
distributed.
The =posterior mesenteric plexus= (P. mesentericus caudalis) accompanies
the artery of like name in its distribution.
The secondary plexuses which accompany the branches of the mesenteric
arteries give off branches which form two fine peripheral plexuses in
the wall of the intestine. One of these, the =myenteric plexus= (P.
myentericus) or plexus of Auerbach, lies between the layers of the
muscular coat, and is provided with microscopic ganglia. The other is
in the submucous tissue, and is therefore termed the =submucous
plexus= (P. submucosus) or plexus of Meissner.
The following paired plexuses are derived mainly from branches of the
cœliac and aortic plexuses:
1. The =renal plexuses= (P. renales) proceed largely from the
cœliaco-mesenteric ganglia, but receive fibers also from the small
splanchnic nerves. They enlace the renal arteries and supply the
kidneys. Minute renal ganglia occur on the course of the nerves along
the renal vessels.
2. The =adrenal plexuses= (P. suprarenales) are formed by a relatively
very large number of fine fibers derived in great part directly from the
cœliaco-mesenteric ganglia. Numerous minute ganglia occur in their
meshes.
3 _a_. The =spermatic plexuses= (P. spermatid) proceed largely from the
aortic and renal plexuses. Each accompanies the corresponding (internal)
spermatic artery to the testicle.
3 _b_. The =utero-ovarian plexuses= (P. ovarici) are the homologues in
the female of the preceding. They accompany the utero-ovarian arteries
to the ovary and the cornua of the uterus.
The =hypogastric= or =pelvic plexus= (P. hypogastricus) is the pelvic
continuation of the aortic and posterior mesenteric plexuses. The chief
nerves which form it enter the pelvic cavity ventral to the large
vessels, anastomose with each other and with branches from the third and
fourth sacral nerves, and ramify on the pelvic viscera. The peripheral
plexuses derived therefrom are named according to the organs which they
supply; the chief of these are the =hæmorrhoidal=, =vesical=,
=uterovaginal=, =prostatic=, =cavernous= (of the penis or clitoris).