| Umbilical Cord
The umbilical cord has two arteries and one vein, and it is a component of the fetal membrane. Oxygenated blood from the mother enters the fetal circulation through the umbilical vein. Shunts allow most of the blood in the fetal circulation to bypass the fetal liver and lungs. The deoxygenated blood returns to the maternal circulation through the umbilical arteries. While flowing through the fetus, the blood goes first from the placenta to the fetal portal vein branches, to the ductus venosus (which carries 50% of the umbilical vein blood) to the inferior vena cava and right atrium, through the patent foramen ovale, to the carotid and coronary arteries. The ductus arteriosus is another shunt that carries blood from the pulmonary artery to the aorta, bypassing the lungs. Upon birth, the shunts close and the neonatal blood flows through the lungs for oxygenation. [1] |