Observations on the phrenic nerves and the ductus venosus in human embryos and fetuses

Abstract

The phrenic nerves, celiac plexus, and portions of the vagus nerves were studied in human embryos and fetuses which had been sectioned serially and stained with silver. The phrenic nerve gives off a branch to the plexus of nerves along the internal thoracic (mammary) artery. In some instances, a small ganglion was observed in the path of the phrenic nerve in the neck. In the root of the neck, communicating branches from the sympathetic trunk and ganglia were seen to join the phrenic nerves. Nerve bundles are described which pass between the celiac plexus and branches of the phrenic nerves in the diaphragm. Routes for fibers to pass from these nerves in the diaphragm to the sphincter of the ductus venosus are also described, as well as a route for nerve fibers from the vagal trunks to this sphincter. The significance of these findings is discussed.