<P> Blood from the placenta is carried to the fetus by the umbilical vein . In humans , less than a third of this enters the fetal ductus venosus and is carried to the inferior vena cava , while the rest enters the liver proper from the inferior border of the liver . The branch of the umbilical vein that supplies the right lobe of the liver first joins with the portal vein . The blood then moves to the right atrium of the heart . In the fetus , there is an opening between the right and left atrium ( the foramen ovale ) , and most of the blood flows through this hole directly into the left atrium from the right atrium , thus bypassing pulmonary circulation . The continuation of this blood flow is into the left ventricle , and from there it is pumped through the aorta into the body . Some of the blood moves from the aorta through the internal iliac arteries to the umbilical arteries , and re-enters the placenta , where carbon dioxide and other waste products from the fetus are taken up and enter the maternal circulation . </P>
<P> Blood from the placenta is carried to the fetus by the umbilical vein . In humans , less than a third of this enters the fetal ductus venosus and is carried to the inferior vena cava , while the rest enters the liver proper from the inferior border of the liver . The branch of the umbilical vein that supplies the right lobe of the liver first joins with the portal vein . The blood then moves to the right atrium of the heart . In the fetus , there is an opening between the right and left atrium ( the foramen ovale ) , and most of the blood flows through this hole directly into the left atrium from the right atrium , thus bypassing pulmonary circulation . The continuation of this blood flow is into the left ventricle , and from there it is pumped through the aorta into the body . Some of the blood moves from the aorta through the internal iliac arteries to the umbilical arteries , and re-enters the placenta , where carbon dioxide and other waste products from the fetus are taken up and enter the maternal circulation . </P>
where does the umbilical vein enter the circulation of the fetus
where does the umbilical vein enter the circulation of the fetus
the portal vein
the portal vein