All About Blood

All About Blood You may not give much thought to your blood (until you cut your finger or scrape your shin). But what exactly is this magical fluid? It’s a little more complicated than you might think. Blood isn’t just one “thing,” but is instead made up of multiple components, each with a specific function. Here’s a rundown of the primary parts of blood, and what they do in your body.

PLASMA, the fluid portion, makes up about 55 percent of your blood. Composed mostly of water and salts absorbed through the digestive system, plasma is the transportation system, the mechanism by which other elements of blood are carried through the body’s vessels. Plasma circulates nutrients and hormones throughout the body, and carries away waste products generated by cells.

RED BLOOD CELLS, also called erythrocytes, make up about 45 percent of blood. Their production is regulated by a hormone that signals bone marrow to start the production lines. Marrow, the soft, spongy tissue inside bones, contains specialized cells called “stem cells” that have the potential to develop into red cells, white cells and/or platelets as needed. Once red blood cells are produced in the marrow, they’re released into the bloodstream, where they have an average life span of about four months. When they’re no longer able to function, the spleen absorbs them and recycles their iron so it’s available to generate fresh young red blood cells.

WHITE BLOOD CELLS, also called leukocytes, are much fewer in number than red blood cells, accounting for only about 1 percent of your blood. But they’re crucial in the body’s immune system. Different types of white blood cells protect your body against illness and infections, flowing through your bloodstream and fighting off viruses, bacteria and other foreign invaders. Like red blood cells, white blood cells are produced in bone marrow.

PLATELETS, or thrombocytes, make up the remainder of the blood and, like red and white cells, are produced in bone marrow. These tiny, plate-shaped cells are key in blood clotting; if you cut your finger, platelets rush to the site of injury and form a plug, or clot, to stop bleeding and begin the healing process at the source of the wound.

Now, here’s how iron fits in to red blood cell production (in technical terms, called erythropoiesis). When you eat iron in foods or take a supplement, it’s absorbed through the gastrointestinal tract; from there, it binds to a specialized carrier protein called transferrin, which delivers it to all the cells in the body. The bulk—about 80 percent—is delivered to the bone marrow, where it’s used to make red blood cells.

And iron isn’t the only nutrient needed for red blood cell production; vitamin B12 and folate also play important roles. Folate works closely with B12 in making red blood cells and helps iron function properly in the body—so if you’re considering an iron supplement, it should contain all three.