Oxygenated blood from fetus is carried by:
**Core Concept**
The question is testing the understanding of the circulatory pathway of oxygenated blood in the fetus. The underlying physiological principle is the unique fetal circulation that allows for the exchange of oxygen and nutrients between the mother and the fetus.
**Why the Correct Answer is Right**
In the fetus, oxygenated blood from the mother is carried to the fetus through the umbilical vein. This oxygenated blood then enters the ductus venosus, which is a shunt that directs the oxygenated blood to the inferior vena cava. From there, it is carried to the right atrium and then to the left atrium through the foramen ovale, which is a patent foramen ovale in the fetus. The oxygenated blood then enters the left ventricle and is pumped to the aorta, which supplies oxygenated blood to the rest of the fetus.
**Why Each Wrong Option is Incorrect**
**Option A:** This is a distractor that is not relevant to the circulatory pathway of oxygenated blood in the fetus.
**Option B:** This is a distractor that is not correct; the ductus arteriosus is a shunt that allows blood to bypass the lungs in the fetus, not carry oxygenated blood.
**Option D:** This is a distractor that is not relevant to the circulatory pathway of oxygenated blood in the fetus.
**Clinical Pearl / High-Yield Fact**
The foramen ovale is a patent foramen ovale in the fetus, which allows oxygenated blood to bypass the lungs and enter the left atrium. This shunt closes after birth when the pressure in the left atrium increases and the right atrium decreases.
**Correct Answer:** C. Ductus venosus