Comparative anatomy and ontogeny of the ductus arteriosus, a vascular outsider

In its function of separating pulmonary and systemic arterial blood flow, t he ductus arteriosus, which connects both circuits, either closes permanent ly at a certain stage in development or attains a capacity to close and reo pen depending on the physiological needs in certain species. In air-breathi ng vertebrates varying from lungfish to mammals, the ductus arteriosus deri ves from the sixth pharyngeal arch artery, and in preparation for its speci fic task, undergoes its own unique differentiation programme, starting earl y in development. To date, the mechanisms involved in defining this unique status, as compared to the other great arteries, are unclear. This re-view clarifies some of the elusiveness of the ductus arteriosus. It includes a c omparative description of this artery in species exemplifying the different classes of air-breathing vertebrates, and illustrates similarities and dif ferences in morphogenesis and closure Mechanisms among the species. It also deals with possible influences of vascular innervation and with congenital anomalies in which the ductus arteriosus is involved. New data suggest tha t HOXB5 expression in the neural crest along the dorsal half of the sixth a rch artery may be involved in the instigation of ductus arteriosus differen tiation.