Oxygenated blood to the fetus is carried by-

Ans. is 'b' i.e., Umblical vein Fetal circulation o Fetal circulation differs from adult circulation in several ways. Almost all differences are attributable to the fundamental difference in the site of gas exchange. o In the adult gas exchange occurs in the lungs, while in the fetus placenta provides the exchange of gases and nutrients. Course of fetal circulation A) Blood returing to hea o Blood oxygenated in the placenta returns by way of the umblical vein, which enter the fetus at the umblicus and course through to join the poal vein. o The ductus venous is a bypass shunt between poal vein and IVC. o Most of the umblical venous blood shunts through the ductus venosus to the IVC. o Blood from IVC (which carries the blood drained from lower extremities, umblical veins, hepatic veins and renal veins) enters the right atrium. o On reaching the right atrium, about 1/3rd of total inferior vena caval return of blood enters the left atrium through formen oval. o The rest two third mixes with the venous return from SVC (which carries the blood drained from head, neck and upper limbs) to enter the right ventricles. B) Blood coming out of the hea Right side o The right ventricle pumps out the blood into pulmonary trunk -4 very small amount of this blood enters the pulmonary circulation because the lungs are collapsed and pulmonary vascular resistance is high. o Most of this blood passes to desending aoa through ductus aeriosus, a shunt between pulmonary trunk and desending Aoa. o Descending aoa carries blood to umblicus through umblical aery, for oxygenation. o Descending aoa also supplies the blood to lower lumbs, kidney and abdominal viscera. Left side o The left ventricle pumps blood into the ascending aoa for distribution in coronary circulation, head and upper limbs.