What is the pathway that an oxygen molecule takes when it enters the blood stream?
1) Deoxygenated blood enters the heart through the vena cava, which then enters the right atrium of the heart and flows through the tricuspid valve into the right ventricle. 2) It is pumped through the pulmonary semilunar valve into the pulmonary arteries which go to the lungs. 3) Breathe in, air goes into your lungs and fills alveoli. The concentration gradient allows O2 to diffuse into the blood and CO2 to diffuse out of the blood. 4) Pulmonary veins return the now oxygenated blood to the heart, where it enters the left atrium before flowing through the mitral valve into the left ventricle. 5) Finally, the oxygenated blood from the left ventricle is pumped out via the aorta, and on to the rest of the body, where oxygen is used as the terminal electron acceptor in chemiosmosis (the final stage of aerobic respiration) where most ATP is produced. Most O2 will not return to the lungs. Hope this is understandable!
