Cardiovascular system

The answer is 1 and 3 only. I can’t figure out why No 1 is correct and No 2 is wrong.

Number 2 is definitely wrong because: not ALL the blood flowing from the lungs goes to the kidneys. While it is true that blood needs to be filtered, the blood flowing to the kidney to be filtered is coming from the body, yet the lungs send the blood to the left atrium and ventricles first, from here blood is bumped through the aorta to the rest of the body. What reaches the kidneys is only 20% of the output and it reaches it from the abdominal aorta. Hence, not ALL the blood from the lungs passes by the kidneys because it reaches other organs too.

Choice 1 is correct because: Blood first reaches the heart form the lungs for the first time in the left atrium and ventricle, then it goes to the rest of the body, but then AGAIN it comes to the heart a SECOND time to the vena cava and right atrium and ventricle. Hence, each one bump from the lungs passes by the heart TWICE, once oxygenated (left atrium and ventricle) and once deoxygenated (right atrium and ventricle).

Hope this helps

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Thank you!That helps me a lot.

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