Blood Summary Your blood is living tissue made up of liquid and solids. The liquid part, called plasma, is made of water, salts, and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells, and platelets. Red blood cells (RBC) deliver oxygen from your lungs to your tissues and organs. White blood cells (WBC) fight infection and are part of your body’s defense system. Platelets help blood to clot when you have a cut or wound. Bone marrow, the spongy material inside your bones, makes new blood cells. Blood cells constantly die and your body makes new ones. Red blood cells live about 120 days, and platelets live about 6 days. Some white blood cells live less than a day, but others live much longer. Blood tests show whether the levels of substances in your blood are within a normal range. They help doctors check for certain diseases and conditions. They also help check the function of your organs and show how well treatments are working. Some of the most common blood tests are blood count tests, which measure the number, size, and shape of cells and platelets in the blood. Problems with your blood may include bleeding disorders, excessive clotting and platelet disorders. If you lose too much blood, you may need a transfusion. National Heart, Lung, and Blood Institute Encyclopedia Arterial stick Blood typing Capillary sample Cord blood testing Venipuncture Reference Desk Biology of Blood Merck & Co., Inc. Hematology Glossary American Society of Hematology Teenagers Blood Nemours Foundation Blood Types Nemours Foundation Start Here Blood (For Parents) Nemours Foundation Blood Basics American Society of Hematology Blood Tests National Heart, Lung, and Blood Institute What Is Blood? America’s Blood Centers Related Issues Blood and Diversity American Red Cross Games Blood Type Game American Red Cross Play the Blood Typing Game Nobel Foundation Specifics Blood Types American Red Cross Clinical Trials ClinicalTrials.gov: Blood Cells National Institutes of Health Find an Expert Find a Hematologist American Society of Hematology National Heart, Lung, and Blood Institute National Heart, Lung, and Blood Institute Journal Articles Blood Array Red blood cell production Children What’s Blood? Nemours Foundation
