Absent and abnormal umbilical arteries

Abstract

Umbilical arteries were not found in some fetuses from female rats given retinoic (vitamin A) acid by gavage on day 10 of gestation. It was felt that fetomaternal exchange in them must have been maintained either by the vitelline placenta alone, or by the allantoic placenta supplied by branches of the vitelline artery. In control rat embryos the vitelline and umbilical arteries communicated until day 11 after which the two circulations became separate. In young from females given retinoic acid during gestation, however, this communication (vitelloumbilical anastomosis) persisted and the definitive umbilical arteries failed to develop completely. This resulted in the normally formed single umbilical artery of the cord and its branches to the allantoic placenta receiving blood from the aorta through the vitelline or superior mesenteric artery. Thus, although the intra‐abdominal portions of the umbilical arteries were missing, the allantoic placental circulation was maintained. The vitelline placental circulation was normal. In other experimental embryos persistent primary umbilical arteries were frequently seen alone or accompanied by definitive umbilical arteries. In normal human embryos a vitelloumbilical anastomosis apparently does not form and the single umbilical artery seen in fetuses with symmelia is most likely a persistent primary umbilical artery, as suggested by Dawson. However, the possibility of a vitelloumbilical anastomosis occasionally arising as an abnormality in human embryos cannot be overlooked.

A clinical and experimental overview of sirenomelia: insight into the mechanisms of congenital limb malformations

“…These mutants have severe cardiac malformations and an absence of major vessels owing to defective formation of the primitive capillary plexus. Interestingly, the administration of RA to pregnant rats causes abnormal development of the umbilical and vitelline arteries that are comparable to those reported in human sirenomelia (Monie and Khemmani, 1973). Further studies on the function of RA in chick and mouse embryos (Hochgreb et al, 2003; Lai et al, 2003) showed that RA negatively regulates endothelial cell proliferation, allowing the premature coalescence and differentiation of precursors, thereby interfering with vascular remodeling.…”

“…By E8.5, the umbilical artery, which originally forms in association with the allantois, fuses to the recurved distal portions of the dorsal aortas, temporally connecting the vitelline and umbilical vasculature. Subsequently, the vitelline artery discontinues its connection with the umbilical artery while connecting dorsally with the abdominal aorta (Monie and Khemmani, 1973; Garcia-Porrero et al, 1995). Consequently, the umbilical artery pumps blood from the embryo to the placenta while the vitelline artery carries blood from the embryo to the yolk sac and eventually becomes remodeled to form the intestinal arteries.…”

Anatomy and Pathology of the Umbilical Cord and Major Fetal Vessels

“…The dispute is not totally resolved, however, as studies in mice with this anomaly suggest the vessel to be allantoic in nature; it is thought only to take an abnormal course, with fusion of the two arteries (Schreiner & Hoornbeek, 1973). How complex these embryological considerations are can be seen in the study by Monie and Khemmani (1973). They induced SUA in rat fetuses with retinoic acid and described the vitelloumbilical anastomosis in the embryos.…”

Comparative development of the nervous, respiratory, and cardiovascular systems.

“…In rat, mouse, and probably other rodents, there is a transient communication between the vitelline and umbilical arteries within the embryo until day 11, when it disappears (30). Persistence of this channel results in bizarre patterns of the two arteries it connects.…”