- Reticulocytes: After about four days of differentiation and hemoglobin production, the erythroglast sheds its nucleus and becomes a reticulocyte. After spending two more days in the bone marrow, the reticulocyte enters the circulation where, twenty-four hours later, they complete their maturation and become indistinguishable from other mature RBCs. An elevated reticulocyte count indicates bleeding. Normal range is from 0-1.5%.
- Red blood cells (erythrocytes, corpuscles): Mature erythrocytes have no nuclei, and consist mainly of hemoglobin in a supporting framework called stroma. Erythrocyte formation takes place in the red bone marrow of the adult and in the liver, spleen, and bone marrow of the fetus. This formation requires ample supplies of such dietary elements as iron, cobalt, copper, amino acids, and certain vitamins. The main function of RBCs is in the transportation of oxygen and carbon dioxide. They are also important in the maintenance of a normal acid/base balance. Since they also help to determine the viscosity (a tendency to resist flow) of the blood, RBCs influence its specific gravity. During its 120-day life, a red blood cell makes about 75,000 round trips between the lungs and tissues. At the end of their life, they return to the bone marrow where they are removed by the reticuloendothelial system (particularly the liver, bone marrow, and spleen). Despite the constant destruction and production of RBCs (about 300 billion are destroyed and replaced each day), the body is able to maintain a fairly constant number. A decreased number usually indicates some form of anemia.
