Topography of the pelvic autonomic nerves in human fetuses between 21-29 weeks of gestation

Summary A topographical study concerning the autonomic nerves in the pelvis of human fetuses was performed by investigating 300–600 m thick sections through fetal pelves, impregnated with the epoxy resin E 12 and cut with a diamond wire-saw. In addition the inferior hypogastric plexus of a 26-week old male fetus was dissected by lateral approach. In 21–29-week old fetuses the pelvic autonomic nerves are relatively thick. Thus the nerves stand out well against surrounding structures and their topographical relationships can exactly be determined. The inferior hypogastric plexus of 21–29-week old fetuses is situated on a curved line between the rectum and the ventrally adjacent structure. It constitutes a rectangular plate, which cannot be subdivided into individual plexuses for the different pelvic organs. The fetal plexus is heavily ganglionated. Large ganglia, forming the so-called ganglion of Frankenhaeuser, are found in the female as well as in the male fetus. In the fetal pelvis the connective tissue compartments are still clearly arranged, because adipose tissue is not yet abundant. The greater part of the inferior hypogastric plexus is situated exactly at the border between a dense visceral tissue medially and a loose parietal tissue laterally. The plexus does not share a common connective tissue cover with the pelvic blood vessels. In fetuses the inferior hypogastric plexus lies in close vicinity to serveral organs, but the pelvic floor is the only region where the nerves can hardly be separated from the surrounding structures.