The animation is dedicated to the fetal circulation criteria of blood composition.

1) Direction of oxygenated blood

The first diagram details more than 30 blood vessels, structures and organs involved in fetal blood circulation. The placenta is connected with the vena cava (i.e. the heart) via the umbilical and hepatic veins. The heart is schematically represented. The septum primum, foramen ovale and septum secundum are clearly indicated along with the pulmonary trunk, ductus arteriosus, aorta and umbilical arteries.

The animation starts with the blood, which leaves the placenta and moves through the umbilical vein toward the liver. The blood then passes through the ductus venosus and enters the inferior vena cava. From here, blood flow is directed by the valve of the inferior vena cava through the right atrium toward the foramen ovale. In the next sequence, blood flow is separated by the crista dividens, so that the major portion of oxygenated blood passes directly into the left atrium; a small portion of oxygenated blood remains in the right atrium. Next, the blood passes through the left ventricle and into the aorta. Some of the blood then moves through the brachiocephalic artery, left common carotid artery and left subclavian artery toward the brain and the cranial part of the body. The rest of the blood enters the descending aorta.

2) Direction of the deoxygenated blood

A diagram indicates the deoxygenated blood with a black line.

From the brain, the deoxygenated blood enters the right atrium, mixes with a small amount of oxygenated blood (which was previously separated by the crista dividens) and penetrates the right ventricle. Then, blood enters the pulmonary trunk and moves into the ductus arteriosus, where deoxygenated and oxygenated blood mix.

3) Direction of the mixed blood

A diagram shows the flow of blood through the descending aorta into the capillaries of the inferior part of the body and the umbilical arteries. From the arteries, the mixed blood enters the placenta. A small amount of blood passes through the capillaries and into the vena cava, where it mixes with the oxygenated blood.

4) Circulatory changes at birth

Brusque ventilation of the lungs decreases pulmonary vascular resistance and increases pulmonary blood flow. The next 13 diagrams illustrate all of the events that take place during the successive circulatory changes at birth. The last diagram summarizes the definitive blood circulation circuit.

(This animation is essential for students of medicine, veterinary medicine, biology and for departments of anatomy, histology, embryology, physiology and cell biology; it is also recommended the students of stomatology, departments or clinics of physiology, pediatrics, cardiac and pediatric surgery, obstetrics and gynecology and schools for midwives.)