Relationship in the chick of the developing pulmonary vein to the embryonic systemic venous sinus

Previous studies have shown that the relationship of the systemic venous si nus (sinus venosus) to the developing pulmonary vein are very similar in mi ce, rats, and man, with the pulmonary vein gaining access to the heart thro ugh a persisting segment of the dorsal mesocardium. It has been suggested t hat this process differs in avian development, with the pulmonary vein bein g connected to the systemic venous sinus with subsequent transfer to the le ft atrium. Here we have investigated the anatomical sequence of events in t he chick, using serial histological sections and microdissection followed b y scanning electron microscopy. We examined a temporal series of chick embr yos, ranging from Hamburger and Hamilton stage 15 to stage 30. Although the re are some differences in detail, the development of the pulmonary venous connections in the chick was found to be directly comparable to that alread y described in eutherian mammals. In both mammals and the chick, the dorsal mesocardial connection, which connects the primitive atrium to the posteri or thoracic wall, forms a fixed point through which the pulmonary vein gain s access to the atrial compartment of title heart, only varying if the conn ection itself is anomalous. The tributaries of the systemic venous sinus an d the primary atrial septal structures develop around the dorsal connection . Anat Rec 259:67-75, 2000. (C) 2000 Wiley-Liss, Inc.