CVS Practice Test 2025 – Complete Exam Preparation

The foramen ovale is a crucial fetal shunt that facilitates blood flow during fetal development. In the womb, the fetus does not use its lungs for oxygenation; instead, oxygenated blood is delivered from the placenta through the umbilical vein to the right atrium of the heart. The foramen ovale is an opening between the right and left atria that allows oxygen-rich blood to bypass the lungs by flowing directly from the right atrium to the left atrium. This is essential because the lungs are non-functional during fetal life and filled with fluid.

After birth, with the initiation of breathing and the establishment of normal pulmonary circulation, the pressure in the left atrium increases, causing the foramen ovale to close and eventually become the fossa ovalis, thus redirecting blood flow to the lungs for oxygenation.

The other structures mentioned do not function as shunts in the same manner during fetal development. The superior vena cava is a major vein that carries deoxygenated blood from the upper body to the right atrium. The coronary sinus also drains deoxygenated blood from the heart itself into the right atrium, and the aortic arch is part of the systemic circulation that carries oxygenated blood away from the heart to