This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
[{'content': 'Oxygenated blood to the fetus is carried by – \nSelect and explain. \nA. Umblical artery, B. Umblical vein, C. SVC, D. Pulmonary artery', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Fetal circulation\n\nFetal circulation differs from adult circulation in several ways. Almost all differences are attributable to the fundamental difference in the site of gas exchange.\nIn the adult, gas exchange occurs in the lungs, while in the fetus placenta provides the exchange of gases and nutrients.\n\nThe course of fetal circulation\nA) Blood returning to the heart\n\nBlood oxygenated in the placenta returns by way of the umbilical vein, which enter the fetus at the umbilicus and course through to join the portal vein.\nThe ductus venous is a bypass shunt between the portal vein and IVC.\nMost of the umbilical venous blood shunt through the ductus venosus to the IVC.\nBlood from IVC (which carries the blood drained from lower extremities, umbilical veins, hepatic veins and renal veins) enters the right atrium.\nOn reaching the right atrium, about 1/3rd of total inferior vena caval return of blood enters the left atrium through formen oval.\nThe 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.\n\nB) Blood coming out of the heart\n1. Right side\n\nThe right ventricle pumps out the blood into pulmonary trunk very small amount of this blood enters the pulmonary circulation because the lungs are collapsed and pulmonary vascular resistance is high.\nMost of this blood passes to descending aorta through ductus arteriosus, a shunt between pulmonary trunk and descending Aorta.\nThe descending aorta carries blood to umbilicus through the umbilical artery, for oxygenation.\nDescending aorta also supplies the blood to lower limbs, kidney and abdominal viscera.\n\n2. Left side\n\nThe left ventricle pumps blood into the ascending aorta for distribution in the coronary circulation, head and upper limbs.', 'role': 'assistant'}]