Whole blood consists of 3 types of blood cells, suspended in a liquid called plasma. Blood circulates through the arteries and veins with each of the blood cell types -- red blood cells, white blood cells and platelets -- performing different functions throughout the body.
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Red Blood Cells
Red blood cells, also called erythrocytes, make up about 40 to 50 percent of the total blood volume. Levels vary for men and women, with men having 5 to 6 million erythrocytes per cubic millimeter of whole blood and women having 4 to 5 million per cubic millimeter. Red blood cells live for approximately 120 days before being replaced by new cells produced in the bone marrow. The red color comes from a pigmented molecule, called hemoglobin, inside red blood cells. Red blood cells carry oxygen throughout the body and deliver carbon dioxide from tissues to the lungs to be exhaled.
White Blood Cells
White blood cells, also called leukocytes, are much fewer in number than red blood cells. There are 5 different types of white blood cells that work together to protect the body by attacking foreign invaders, including bacteria, viruses and tumors. The most common type of white blood cells are called neutrophils. All types of white blood cells are produced in the bone marrow.
Platelets, also called thrombocytes, are cell fragments rather than whole cells. They clump together and form blood clots after an injury. Clots act as plugs to stop bleeding and serve as a base for new tissue growth and healing in the injured area. Certain blood-thinning medications reduce the risk of abnormal blood clots by interfering with platelet function.