Jennifer Gallion, age 15, of Gulfport, Miss., for her question:
HOW IS BLOOD PLASMA IMPORTANT?
Plasma is the liquid part of the blood. This straw colored fluid makes up about 55 percent to 65 percent of the total volume of blood. Plasma is important because it suspends the red and white cells as well as the platelets.
Plasma is made up mostly of water. However, it also contains hundreds of other substances including protein, digested food, waste products and minerals.
The major proteins in plasma are albumin, fibrinogen and globulin. Albumin helps keep plasma in the blood vessels. Fibrinogen plays an important role in clotting, the process by which blood forms a seal over a wound. Globulin proteins, particularly the gamma globulin, helps fight infection.
Digested food enters the plasma from the intestines. The blood carries the food to the body cells, which use it to produce energy and new tissue.
Waste products are picked up from the cells by the blood. The plasma carries many of these wastes, including urea and ammonia. The kidneys and the liver remove wastes from the plasma.
Plasma also contains various minerals and dissolved gases. In addition, it carries chemical substances called hormones from one part of the body to another.
The amount of blood in a person's body depends on the size and the environment of the individual. An adult who weighs 160 pounds has about five quarts of blood. An 80 pound youngster has about half this amount while a nine pound baby will have only about 10 ounces of blood.
People who live in high altitudes where there is less oxygen than on lower levels may have as much as two quarts more blood than their sea level dwelling relatives. The extra blood helps capture much needed oxygen.
Blood is the life stream of the human body.
Along with plasma, blood also contains red blood cells, white blood cells and platelets. These last three items are called "formed elements" because they have definite shapes. The red and white blood cells are sometimes called corpuscles.
Red blood cells, also called erythrocytes, are the most numerous of the formed elements. Each microliter of blood contains from 4 to 6 million red blood cells.
The main job of red blood cells is to carry oxygen from the lungs to the body tissues and to carry carbon dioxide from the body tissues to the lungs.
White blood cells, also called leukocytes, help protect the body against disease and infection. A microliter of blood contains from 4,000 to 10,000 white blood cells.
Platelets are disc like structures that develop from cells produced in the bone marrow. They help prevent the loss of blood from damaged vessels. If a small blood vessel is cut or broken, platelets stick to the damaged surface and to one another. As they pile up, they form a temporary seal over the injury.
Platelets are the smallest of the formed elements. A microliter of blood contains from 150,000 to 400,000 platelets.