<prompt> Oxygenated blood to the fetus is carried by-Umblical aeryUmblical veinSVCPulmonary aery  <response>: 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 13rd 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. 