[New knowledge concerning "Hoboken's valves" of the umbilical artery].

From the time of the first description, in the seventeenth century, of valvular structures ("Hobokensian valves") in the arteries of the umbilical cord their existence has remained challenged and their function still remains unclear. In order to investigate the arteries in the human umbilical cord, as well as the existence and construction of the Hobokensian valves two experiments were carried out: on the one hand, segments of the human umbilical cord were ligatured bilaterally and fixed in varying time intervals ranging from a few seconds to three minutes post natal, on the other hand one hour post natal umbilical cord arteries were dilated by the use of radio opaque material by applying increased pressure, X-rayed and fixed. The fixed preparations were rasterelectronically and photoelectrically examined and a graphic reconstruction of the arterial wall from the segmental samples was carried out. The wide umbilical cord artery consists of endothelium and double-layered media: the smooth muscle cells of the inner layer are ordered in a scissor-like lattice, the outer layer is constructed of right and left revolving screw-like intersecting muscular fascicules. In the first minutes after birth, due to localised contractions of the double-layered media, numerous waist-formed grooves of the whole arterial wall appeared, which correspond to the Hobokensian valves. They form the initial stage of a contraction process, which leads onto active luminal occlusion and interrupts the perfusion of the umbilical cord. Due to the passage-like appearance of the "Hobokensian valves" the controversial views concerning their existence are clarified.