You know what blood is — it's that red stuff that oozes out if
you get a paper cut. The average person has about 1 to 1½
gallons (4-6 liters) of it. But what is blood, really, and where
does it come from? How Does the Body Make Blood? It's not made
in a kitchen, but blood has ingredients, just like a recipe. To
make blood, your body needs to mix: red blood cells, which carry
oxygen throughout the body white blood cells, which fight
infections platelets, which are cells that help you stop
bleeding if you get a cut plasma, a yellowish liquid that
carries nutrients, hormones, and proteins throughout the body
Your body doesn't go to the store to buy those ingredients. It
makes them. Bone marrow — that goopy stuff inside your bones —
makes the red blood cells, the white blood cells, and the
platelets. Plasma is mostly water, which is absorbed from the
intestines from what you drink and eat, with the liver supplying
important proteins. Put all these ingredients together and you
have blood — an essential part of the