In the lungs, the pulmonary arteries (in blue) carry unoxygenated blood from the heart into the lungs. Throughout the body, the arteries (in red) deliver oxygenated blood and nutrients to all of the body's tissues, and the veins (in blue) return oxygen-poor blood back to the heart.
The water is able to leave in and out of the cells because there is a cell membrane splits the bilayer of tissue and then the water start leaving and coming back in again from the stage of osmosis.
