The Probert Encyclopaedia of Medicine

ERYTHROCYTES

Erythrocytes or red blood cells, carry 99% of the oxygen the body needs. Although plasma circulates throughout the body, it can only carry about one percent of the oxygen that the body needs. Red blood cells are the most abundant cells in the body, constituting about 45% of the blood. Their main function is to carry oxygen to tissue and remove carbon dioxide waste. Red blood cells are mainly made of water and hemoglobin, an iron- containing protein. Hemoglobin gives red blood cells their colour and is so highly concentrated in individual cells that it almost forms crystals. It is an important protein in the transport of oxygen and carbon dioxide. Red blood cells are manufactured in myeloid tissue, better known as red bone marrow. It is found mainly in the sternum, ribs, and cranial bones, although a few other bones also contain small amounts of the tissue. Each cell is very small, about .008 centimeter in diameter and shaped like a round cushion, with a hollow on each side. The rate of red cell formation is regulated by a messenger hormone called erythropoietin which is
produced in the kidneys. This hormone signals the cell to begin growth. First, the cell splits in two. Each of the pair in turn divides until there are sixteen red blood cells. Inside each of the cells hemoglobin is being produced. This production continues until the concentration of the protein becomes 95% of the dry weight of the cell. As this saturation point nears, the cell expels its nucleus, taking on a biconcave shape and thus, increasing its oxygen- carrying potential. At this point, the cell is called a corpuscle. The production of a corpuscle takes six days to complete. Yet the cell will only live for 120 days. About two and a half million red blood cells are destroyed every second. They are broken down into their constituent parts, some of which can be used again to manufacture new red cells. Normal red blood cell production depends upon the body having an adequate supply of iron and two main vitamins: B12 and folic acid. There are many diseases due to deficiencies in red cells, they are collectively known as anemia. Hemolytic anemia is caused by
excessive destruction of red blood cells. It is often caused by poisoning, or a disease such as malaria, or may be an inherited condition. Pernicious anemia, in which large numbers of abnormally large red cells are made, is due to lack of proper absorption of vitamin B12. It can now be easily controlled with regular injections of the vitamin.
Research Erythrocytes