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THE SYMPATHETIC

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Originally appearing in Volume V19, Page 403 of the 1911 Encyclopedia Britannica.
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THE SYMPATHETIC SYSTEM This system is made up of two gangliated cords running down one on each side of the vertebral column and ending below in the median vertebrae. In addition to these cords there are numerous ganglia and plexuses through which the sympathetic nerves pass on their way to or from the viscera and blood-vessels. A typical ganglion of the sympathetic chain is connected with its corresponding spinal nerve by two branches called rami communicantes, one of which is grey and the other white Hr. Va. 0,P6 (see fig. 4). The white consists of medullated fibres belonging to the central nervous system, and these are splanchnic afferent or centripetal, and efferent or centrifugal. The efferent fibres lie in the anterior roots of the spinal nerves, and, like all the fibres there, are either motor or secretory. They are the motor paths for the unstriped muscle of the vessels and viscera, and the secretory paths for the cells of the viscera. In the course of each fibre from the nerve cell in the spinal cord, of which it is an axon, to the vessel or viscus it supplies, there is always a break where. it arborizes round a ganglion cell, and this may be in its own ganglion of the sympathetic chain, in a neighbouring ganglion above or below, or in one of the so-called col-lateral ganglia interposed between the sympathetic chain and the vis- cera. In addition car, to these there are a From A. M. Paterson, in Cunningham's Text-Book of certain number of Anatomy. vaso-dilator and FIG. 5.-The Distribution of the Symviseero-inhibitory pathetic Gangliated Cord in the Neck. without which cell Sy.I, Superior cervical ganglion, and con- without any cell nexions and branches. connexions from I C Internal carotid. artery. the spinal or cranial Ph, Glosso-pharyngeal. nerve to the viscera. G Va, Vagus. The splanchnic. p l a n c h n i c petal fibres are the Hy, Hypoglossal. afferent or centri- C.i, 2, 3, 4, First four cervical nerves. sensory nerves from Flex, Pharyngeal plexus. the viscera, and G.Fh, Glosso-pharyngeal nerve. have no cell con- E.C, To external carotid artery. nexions until they Sy.2, Middle cervical ganglion,connexions reach the spinal and branches. ganglia on the pos- C.5, 6, InFifth ferior and sixth cervical thyroid rrvicaal nerves. tenor roots of the A V Ansa Vieussenii. spinal nerves, which Sy.3, Inferior cervical ganglion, con-they do by travers- nexions and branches. ing the gangliated C.7, 8, seventh and eighth cervical nerves. cord of the sym- Vert, Vertebral plexus. pathetic. The fibres of the white rami car, Cardiac branches. communicantes are remarkable for their small diameter, and the efferent fibres, at all events, are only found in two regions, one of which is called the thoracico-lumbar stream and extends from the first or second thoracic to the second or third lumbar nerve, while the pelvic stream is found from the second to the fourth sacral nerves. The grey mini communicantes are found in connexion with all the spinal nerves, though they are irregular in the paths by which they reach the sympathetic ganglia from the cells of which they spring; their fibres are mainly non-medullated, and pass into both roots of the spinal nerves and also into the anterior and posterior primary divisions of those nerves. In this way they reach the body wall and limbs, and are somatic vaso-motor, secretory and pilo-motor fibres, supplying the vessels, glands coccygeal ganglion (g. impar). In the neck the cords lie in front of and hair muscles of the skin and its glands. The sympathetic the anterior tubercles of the transverse processes of the cervical I ganglia, from which these nerves come, contain multipolar nerve vertebrae, in the thorax, in front of the heads of the ribs, while cells with one axon and several dendrites as well as a number of in the abdomen they lie in front of the sides of the bodies of the ~ medullated fibres passing through, and much connective tissue. +02 NERVOUS SYSTEM Some of the axons of these cells pass in the connectives to ganglia above and below, while others pass with the splanchnic efferent nerves to the viscera. The above sketch will give the general scheme of the sympathetic system, but its exact topographical details in man must be sought in the modern text-books such as those of Gray, Quain or Cunning-ham. Here only the larger and more important details can be given. In the gangliated chain there is a ganglion corresponding to nearly each spinal nerve, except in the neck, where only three are found; of these the superior cervical ganglion is more than an inch long, and is connected with the first four spinal nerves as well as From A. M. Paterson, in Cunningham's Text-Book of Anatomy. T.1-12, L.i-5, S.1-5, Co, Anterior primary divisions of spinal nerves, connected to the gangliated cord of the sympathetic by rami communicantes, white (double lines) and gray (single lines). Oes, Oesophagus and oesophageal plexus. Ao, Aorta and aorta plexus. Va, Vagus nerve joining oesophageal plexus. S.1, Great splanchnic nerve. X, Great splanchnic ganglion. S.2, S m a 11 splanchnic nerve. S.3, Least splanchnic nerve. Co, Coronary artery and plexus. Spl, Splenic artery and plexus. H, Hepatic artery and plexus. SL, Semilunar ganglion. Di, Diaphragm. S.R, Suprarenal capsule. Re, Renal artery and plexus. S.M, Superior mesenteric artery and plexus. Sp, Spermatic artery and plexus. I.M, Inferior mesenteric artery and plexus. Hy, Hypogastric nerves and plexus. Rec, Rectal plexus. Ut, Uterine plexus. Ves, Vesical plexus. V. V. V, Vis'ceral branches from sacral nerves. with the ninth, tenth and twelfth cranial nerves (see fig. 5, Sy.I). Branches of distribution pass from it to the pharyngeal plexus, the heart and the two carotid arteries. Of these the branch accompanying the internal carotid artery passes to the carotid and cavernous plexuses, and through these communicates with the sphenomaxillary, otic and ciliary ganglia, while the branch to the external carotid communicates with the submaxillary ganglion. The middle cervical ganglion (fig. 5, Sy.2), when it is present, gives rami cornmunicantes to the fifth and sixth cervical nerves, as well as branches of distribution to the thyroid body and heart. The inferior cervical ganglion (fig. 5, Sy.3) lies behind the subclavian artery, and, besides the main connective cord, has a loop(ansa Vieussenii) joining it to the middle cervical ganglion in front of that vessel. It communicates with the seventh and eighth spinal nerves, and gives branches of distribution to the heart and to the subclavian artery and its branches, especially the vertebral. The thoracic part of the sympathetic cord has usually eleven ganglia, which receive both white and grey rami communicantes from the spinal nerves (fig. 6) ; of the former the upper ones run up in the chain and come off from the cervical ganglia as already described, while the lower ones form the three abdominal splanchnics which pass through the diaphragm (q.v.) and join the abdominal plexuses. The great splanchnic (fig. 6, S.1) comes from the sixth to the ninth ganglia, and ends in the semi-lunar ganglion of the solar plexus (fig. 6, SL). The small splanchnic (fig. 6, S.2) comes from the ninth and tenth, or tenth and eleventh ganglia, and ends in the aorticorenal ganglion of the solar plexus, while the smallest splanchnic (fig. 6, S.3) comes from the last thoracic ganglion, whether it be the tenth or eleventh, and ends in the renal plexus. In the lumbar region the gangliated cord is very irregular; there may be four or more ganglia, and these are often fused. Grey rami communicantes are given to all the lumbar spinal nerves, and white ones are received from the first two. Most of the branches of distribution pass to the aortic plexus. The sacral gangliated cord runs down just internal to the anterior sacral foramina; it usually has four small ganglia, and the two cords end by joining the coccygeal ganglion or ganglion impar, though the two-fourth sacral ganglia are united by transverse interfunicular commissures. The white rami communicantes, already mentioned as the pelvic stream, from the second to the fourth sacral spinal nerves, do not enter the ganglia but pass directly to the pelvic plexuses (fig. 6, V). Sympathetic Plexuses.—In the thorax are the superficial and deep cardiac plexuses and the coronary plexuses; the former receives the left superior cervical cardiac of the vagus, and lies in the concavity of the arch of the aorta. The deep cardiac plexus is larger, and lies in front of the bifurcation of the trachea; it receives all the other cardiac nerves, and communicates with the anterior pulmonary plexuses of the vagus (see NERVES: Cranial). The right and left coronary plexuses accompany the coronary arteries; the former communicates with both the cardiac plexuses, the latter only with the deep cardiac plexus. In the abdomen the solar plexus is by far the most important. It lies behind the stomach and surrounds the coeliac axis; in it are situated the semilunar, aortico-renal and superior mesenteric ganglia, and from it are prolonged subsidiary plexuses along the main arteries, so that diaphragmatic, suprarenal, renal, spermatic, coeliac, superior mesenteric, aortic and Inferior mesenteric plexuses, are recognized. The hypogastric plexus is the continuation downward of the aortic, and lies just below the bifurcation of the aorta (see fig. 6, Hy) ; it divides into two branches, which accompany the internal iliac arteries and are joined by the pelvic stream of white rami communicantes from the sacral spinal nerves and some twigs from the ganglia of the sacral sympathetic to form the pelvic plexuses. These are prolonged to the viscera along the branches of the internal iliac artery, so that haemorrhoidal, vesiral, .prostatic, vaginal and uterine plexuses are found. By the side of the neck of the uterus in the last-named plexus several small ganglia are seen. (For the literature of the sympathetic system, see Quain's Anatomy, London, 1895.)
End of Article: THE SYMPATHETIC
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