Going from the alveoli to the pulmonary vein (which is the only vein to carry oxygenated blood) will go back to the heart and dump into the left atrium. It will pass through tricuspid valve into the left ventricle. The left ventricle will forcefully push out the newly oxygenated blood through the aortic valve and to the aorta.
Through the aorta it will descend and bifurcates into the femoral arteries. One on each side. Through there it will go to the popliteal artery (which is behind the knee).
