Cells -> Tissues -> Organs -> Organs systems -> Organisms
The red blood corpuscles have a pigment called hemoglobin that binds to the oxygen and carries it to the whole body in both the conditions, when the body is at rest or when the body is exercising. The oxygenated blood from the heart is carried to the various parts of the body and the de-oxygenated blood from various parts of the body is carried to the lungs where the exchange of gases takes place.
The kidneys is controlled by hormones and by the composition of the urine since the hormone released is called ADH which is produced by the pituitary gland.
