Phrenic plexus

Abstract: T _ HE adrenal gland has associated with it a preponderance of nervous tissue which seems far in excess to that which so small a structure might require. This apparent redundance of nervous tissue can be explained on the basis of two factors. The first of these is most likely related to the ectodermal origin of the medulla. The idea that the adrenal medulla is capable of giving rise to efferent impulses, and thus act as a sort of peripheral nervous center, was proposed by Jacobj (1892), Elliott ('13), Kolmer ('18), and Crile ('31). Rindt and Kahn ('29) could not, however, confirm the findings of the above-mentioned investigators on the neural transmission of adrenalin-invoked impulses. The second of the two factors referred to above is related to the juxtaposition of the adrenal glands to the coeliac plexus. A great portion of the nervous tissue lying in proximity to the adrenals is actually distributed to other organs. The accepted classification of the autonomic nervous system into sympathetic and parasympathetic divisions will be employed. Though for gross anatomical purposes the splanchnic nerve will be classified as sympathetic, the work of Kure and his many co-workers ('28, '30, '31a, '31b, '31d) on the spinal parasympathetic nerves indicates that this nerve contains parasympathetic as well as sympathetic fibers. Hinsey ('33), in the cat, could not, however, confirm the presence of efferent parasympathetic fibers in the dorsal spinal roots, as maintained by Kure. Nor could Hollinshead ('36) find any degeneration in the splanchnic nerve after sectioning the dorsal roots of the lower thoracic and upper lumbar nerves proximal to their ganglia. The coeliac plexus (through which the adrenal receives most of its nerve supply) is commonly referred to as sympathetic in nature. In reality it consists of an admixture of parasympathetic (vagus and Kure's spinal parasympathetics) as well as sympathetic elements. Though the vagus fibers enter the coeliac plexus, they have no functional relationship to the ganglia located therein (Kuntz, 1938). It is because of the sympathetic nature of the coeliac ganglia that the other constituents of this plexus are often erroneously referred to as being entirely sympathetic in nature. The adrenal plexus is referred to as an offshoot of the coeliac plexus. Superiorly the adrenal plexus is continuous with the inferior phrenic plexus, while inferiorly it joins the renal plexus and also the internal spermatic or ovarian plexus on the left side. These gross anatomical features (Fig. 1) have recently been illustrated in detail by Teitelbaum ('33) on the basis of microscopic dissections in infants. The fibers which make up the adrenal plexus are derived from the splanchnic nerve, the sympathetic trunk, the coeliac ganglion, the vagus nerve, and sometimes the phrenic nerve.