To understand how our body makes new blood, we first have to clarify what blood actually is: a liquid without which we cannot live. About five to six liters flow through us, which is roughly the amount of four large water bottles; in children, a little less.
Blood consists of three groups: red and white blood cells and platelets. The white blood cells defend our body against diseases, viruses and bacteria like a kind of shield. The red blood cells act like a mail carrier delivering a package from one place to another. Instead of books or toys, the blood brings oxygen from the lungs to where the body needs it. The platelets work like an ambulance. When we are injured, they cling to the wound, clump together and form a plug that stops the bleeding before a scab forms, under which the wound can heal.
Many people think that the body only makes new blood when a person loses blood—for example because they have been injured. Or when blood has been drawn by the doctor. Or when someone donates blood. In reality, however, our body makes new blood every day, all the time, and sorts old blood into an organ called the spleen.
When We Need New Blood, the Stem Cells Wake Up
Making new blood works like this: In our bones there is soft, sponge-like tissue called bone marrow. The bone marrow can be imagined as a kind of blood-making factory. In this factory work special cells that we call stem cells. Actually, these cells are usually asleep, but when new blood is needed, they wake up and help!
The stem cells can not only reproduce themselves, but also produce new cells that then become mature blood cells. Thus, our body produces many new blood cells every day—about 200 billion, explains Viktoria Flore, who works as a scientist in Berlin researching blood. 200 billion, that is a 2 with 11 zeros.
When the new blood is ready, it is transported through the arteries and veins to the body. These can be imagined as roads that run across the entire body and ensure that everywhere gets enough blood. So that your whole body is also supplied with fresh blood tomorrow.
