Blood:
Blood is a fluid composed of cells and plasma that flow in the arteries and veins of the body. The cellular components of blood are red blood cells, white blood cells and platelets. Plasma is the fluid component of blood that carries red and white blood cells to the body’s organs as well as the nutrients and by-products of metabolism. Red cells, by far the most common cell component in blood, give blood its red color. Red cells contain hemoglobin, a protein that allows red cells to carry oxygen to the tissues and bring CO2 (carbon dioxide) back to the lungs, where the CO2 is exchanged for a new charge of oxygen. White cells are important in fighting infections, while platelets are crucial to proper clotting. Plasma, which contains many proteins, carries nutrients and helps bring the by-products of metabolism to the liver and kidneys for processing or elimination.
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