The only cells in the human body without a nucleus are the red blood cells. They are bright red in color which comes from the oxygen they carry. They have a disk-like shape.
The red cells are minute disc shaped bodies, concave on either side. They are present in very large amount, numbering about 5 millions in adult male and 4.5 millions in adult female per cubic millimeter of blood. The edges are thicker and rounder than the centre and so are concave, but have no nucleus. They contain a special protein known as hemoglobin. This is a pigment, which is yellow in colour, but when seen in masses or bulk, appears to be bright red, which gives a red colour to the blood. The inner and outer layer of the cell is made up of protein and the middle layer of fat.
Hemoglobin
Hemoglobin is a complex protein which contains iron and gives the red colour to the red cells. It has a very strong attraction for oxygen. When the red cells pass through the lungs, the hemoglobin combines with oxygen drawn from the air and forms oxy hemoglobin which becomes bright red in colour. By means of this function, Oxygen is carried to the tissues from the lungs. As the red cell pass through the tissues, oxygen is given off from the blood and the hemoglobin assumes a dull colour, making the blood a dark purplish-red in colour. The amount of hemoglobin present in normal blood is about 13 to 15 gm per 100 ml. of blood.
Development of R.B.C.
The Red cells are produced in the bone marrow of short, filat, irregular bones at the end of the long bones. In the process of development in the bone marrow, the red cells pass through several stages. At first, they are large and contain nucleus, but no hemoglobin. Then they develop into norm oblast which is smaller cells, charged with hemoglobin and a small nucleus. The next stage called as reticulecytes, where the nucleus disintegrates and disappears, but the cytoplasm contains fine threads. Finally, these threads disappear and the fully mature red cell passes into the blood stream. For the normal formation of red blood cells many factors are essential as:
1. Protein is necessary for the manufacture of protoplasm.
2. Iron is necessary for hemoglobin. .
3. Vitamin B12 (Cyanocobalamin) is necessary for the maturation of red blood cells.