Cecelia Ball, Age 11, of DeKalb, Ill., for her question:
HOW IS BLOOD PLASMA IMPORTANT?
Plasma is the liquid part of the blood. This straw colored fluid makes up about 55 to 65 percent of the total volume of blood. Plasma is important because it suspends the red and white blood cells as well as the platelets.
Plasma is made up mostly of water. However, it also contains hundreds of other substances including proteins, 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, help 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 persons'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 child has about half this amount while a 9 pound infant 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 living friends. The extra blood helps capture the oxygen needed by the blood. Blood is the lifestream of the human body.
Along with plasma, blood also contains red blood cells, white blood cells and platelets. These last three items are called "formedelements" because they have definite shapes. The red and white blood cells are sometimes called corpuscules. Red blood cells, also called erythrocytes, are the most numerousof the formed elements. Each microliter of blood contains from 4 million 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 leucocytes, 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. to Mike Booth, age 13, of Miami, Fla., for his question: