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Boning Up on Marrow

You may think of your bones as similar to the girders that support a skyscraper. Like I-beams, they're rigid and strong.

But though bones may appear dense and solid, inside there's plenty going on. Your bones actually contain one of your body's vital organs--bone marrow. Bone marrow produces the major components of your blood--red blood cells, white blood cells, and platelets. Red blood cells carry oxygen to your tissues. White blood cells, also known as leukocytes, help you fight infection. Platelets, usually called "cells," are really a fragment of cells. They help stop bleeding.

All are produced in the spongy bone and cavities inside your bones. All these cavities contain marrow, but only certain bones hold red marrow, the type that produces blood. Another type, yellow marrow, is not involved in blood production. Red marrow is made of blood-forming cells, fat cells, and other tissues. Stem cells in the marrow reproduce to form new cells, some of which remain as stem cells; others change to develop into one of three types of blood cells.

Your marrow produces staggering numbers of blood cells--trillions of new cells every day. Take red blood cells, for example: You produce about three million of them per second.

Even an organ with amazing production capabilities can run into trouble. A low red blood count, or anemia, is a very common and generally treatable malady often caused by iron deficiency. Less commonly, too many red blood cells are produced, a condition called polycythemia. An infection will cause the number of white blood cells in the blood to increase. On the more serious side, bone marrow can be attacked by cancer. Cancer of the bone marrow, or leukemia, may be treated by chemotherapeutic agents and in extreme cases by bone marrow transplants.

A blood test called a complete blood count, or CBC, determines the number, type, size, and shape of all three types of cells.

To keep your bone marrow healthy, keep yourself healthy. Eat a diet that includes plenty of fresh fruits and vegetables, get regular exercise, and avoid smoking.