Short notes on Red Blood Cells or Erythrocytes

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.

4. In addition, small quantities of Vitamin-C, folic acid, the hormone thyroxin and traces of copper and manganese are also necessary.

The average life span of a red cell is about 120 days in human beings. They are destroyed in the reticuloendothelial system of the spleen and liver. During this process, hemoglobin is broken down into its component parts, which are carried to the liver. The Globins (Protein) is returned to the protein stores or is excreted in the urine after further break down. The haem is further split into iron which is stored and used again. The rest of the haem is converted into bile pigments (bilirubin and biliverobin) and is excreted in the faeces. Red cell production and break-down proceed at the same rate, so the number of cells remains constant.

Functions:

The functions of R.B.C.: (Red-blood Corpsules)

1. Mainly respiratory:

The chief function of R.B.C. is gas transport- that is oxygen from the lungs to the tissues and to carry away carbon dioxide from it, back to the lungs for excretion.

2. Acid-base balance:

Red cells help to maintain the acid base balance of the body.

3. Viscosity of blood:

They help to maintain the viscosity of blood.

4. Derived pigments:

Various pigments as bilirubin and biliverdin are derived from the hemoglobin after the degeneration of the red cells.