 This video will cover the following objective. Compare the prenatal pattern of blood flow in a fetus versus that of an infant and describe the anatomical structures in the fetal circulation. Oxygen comes from the maternal blood across the placenta. Oxygen-rich blood drains in the umbilical vein from the placenta into the inferior vena cava. At the liver there is a vascular shunt known as the ductus venosis that allows blood to flow directly from the umbilical vein into the inferior vena cava. The inferior vena cava then drains this oxygen-rich blood into the right atrium where it mixes with deoxygenated blood that's draining through the superior vena cava. Now the blood has an intermediate concentration in the right atrium and that blood is forced down into the right ventricle through the tricuspid valve. But at the same time some of this intermediate oxygen-concentration blood moves from the right atrium directly into the left atrium through an opening known as foramen ovale. Then blood that's pumped out of the right ventricle into the pulmonary trunk can directly flow from the pulmonary trunk into the aorta through an opening known as the ductus arteriosus. Foramen ovale and ductus arteriosus enable blood to bypass the pulmonary circuit moving directly into the systemic circuit because the pulmonary circuit does not function for gas exchange until after birth. Then as blood is flowing through the systemic arteries, one of the systemic arteries is the umbilical artery that carries deoxygenated blood into the placenta completing the circuit. After birth ductus arteriosus will constrict allowing the blood that's leaving the right ventricle to travel into the pulmonary arteries to become oxygenated in the lungs. Similarly the foramen ovale will close after birth leaving only the small remnant known as fasso ovales the indentation in the surface of the right atrium. The umbilical arteries and umbilical veins will also deteriorate after birth. The remnant of the umbilical arteries become the umbilical ligaments and the remnant of the ductus venosis will degenerate becoming the ligament venosum.