Demonstrates the distinct circulatory pathways in the fetal heart, showing preferential delivery of oxygenated blood to the brain and heart.
The circulation of the blood through the heart of the adult and the fœtus is demonstrated by the analysis of X-ray cinematographic films recording the passage of injections of radio-opaque media. In the adult, the blood from both venæ cavæ is seen to pass through the right side of the heart and the pulmonary arteries to the lungs. On returning from the lungs the flow is seen to pass through the left side of the heart into the systemic circulation. In the fœtus, the whole of the superior caval blood is seen to pass into the right ventricle and out through the pulmonary valve into the pulmonary trunk; from this vessel it passes on the one hand into the pulmonary arteries and, on the other, via the ductus arteriosus, into the descending aorta. As the brachio-cephalic artery leaves the aorta proximal to the entry of the ductus arteriosus, the superior caval blood does not pass to the coronary system, the head and fore-limbs. The inferior caval blood has a double course through the heart. The main part goes through the foramen ovale to the left auricle and ventricle, and passes out into the aorta and coronary and brachio-cephalic arteries. Hence, the heart and brain are given preferential treatment with respect to the supply of oxygenated blood coming from the placenta. On the other hand, a minor part of the inferior caval blood passes with the superior caval flow into the right ventricle and out into the pulmonary arteries and, via the ductus arteriosus, into the descending aorta.
Barclay et al. (Fri,) studied this question.