3D reconstruction of the vessels that enter the right atrium of the mouse heart at Theiler Stage 20.

Computer-generated 3D reconstructions of a serially sectioned mouse embryo at Theiler Stage (TS) 20 (E 12-12.5 d.p.c.) were studied. This study investigated the vessels that enter the right atrium of the heart and the drainage of the ductus venosus. It was principally undertaken to allow a comparison to be made between the situation in the mouse and at a comparable stage of human development. Later stages of prenatal development were also studied in the mouse by the analysis of serially sectioned embryos at TS 21-26. As no left brachiocephalic vein forms in the mouse, unlike the situation in the human, the left (cranial) superior vena cava drains via the left common cardinal vein, later to become the coronary sinus, into the floor of the right atrium. It was also noted that unlike the situation in the human, at no stage during the prenatal period does the ductus venosus enter the right atrium. Even shortly before birth, it enters the intra-hepatic part of the inferior vena cava at a considerable distance caudal to the right atrium. This study indicates that the haemodynamics of the prenatal cardiac circulation in the mouse differs significantly from that in the human.