If a molecule of CO₂ released into the blood in your left toe is exhaled from your nose, it must pass through all of the following except
A) the pulmonary vein.
B) an alveolus.
C) the trachea.
D) the right atrium.
E) the right ventricle.

Question

Quizplus · Accepted Answer

Once CO₂ is released into the bloodstream, it travels to the heart via the venous system. It enters the right atrium from the inferior and superior vena cavae, is pumped into the right ventricle, and then is sent to the lungs through the pulmonary artery. In the lungs, the CO₂ diffuses into the alveoli and is eventually exhaled through the trachea and out of the nose or mouth. The pulmonary vein is not a site of gas exchange and therefore would not be involved in the release of CO₂ from the body.

If a Molecule of CO₂ Released into the Blood in Your