Considerations on the phrenic ganglia

Abstract

The phrenic ganglion is described as a small ganglion located at the junction of the right phrenic nerve and branches of the celiac plexus, on the diaphragm. The descriptions of this ganglion are few and incomplete and justify the present study which has been performed macroscopically by dissection and microscopically using silver stained (the method of Bielschowsky) drawn pieces. Dissections of 10 human adult specimens showed one or more ganglia located at the level of the terminal division of the right diaphragmatic artery; these ganglia belong to a trunk linking the right phrenic nerve and the celiac ganglion. In some specimens that nervous trunk was replaced by a ganglionated plexus. That trunk--the diaphragmatic nerve--attaches to a distinctive projection of the celiac ganglion; it may be double, but there is one ganglionated component. No left phrenic ganglia were detected. The macroscopic phrenic ganglia are distributed as follows: the lower to the adrenal gland and the upper to the diaphragm. Microscopically, the ganglia had autonomic characteristics; intrinsic microganglia were also detected within the diaphragmatic nerve. Moreover, periadventitial nervous cells were detected on the right inferior phrenic artery. (1) the phrenic ganglia seem to be constant structures on the right-hand side; (2) their number is variable--it may be the result of individual fragmentation or coalescence during development; (3) these ganglia may be either adrenal vasomotor or diaphragmatic vasomotor, and functionally belong to the celiac plexus; (4) intrinsic neural and periarterial locations are also possible for macroscopically undetectable populations of autonomic nervous cells.