Blood is the reason for the circulatory system. Your heart, veins, and arteries work to keep blood moving throughout your body. Blood may look like a simple red liquid, but it is made up of several different parts. More than half the volume of your blood is made up of a golden colored liquid called plasma. Your blood gets its deep red color from red blood cells. They make up most of the remaining volume of your blood.
Red blood cells are red because of a molecule called hemoglobin. Hemoglobin contains iron. The iron allows the red blood cell to carry gases like oxygen and carbon dioxide. Your heart pumps blood throughout your body. When blood flows to the lungs, oxygen binds to the hemoglobin in red blood cells. Your heart keeps pumping and your blood moves to other parts of your body. Red blood cells deliver oxygen to your cells. .....