Functions of Red Blood Cell

Blood is the life-maintaining fluid that circulates in the body. Blood cells are suspensions of special cells in a liquid called plasma. An adult man has around 5-6 liters of blood in the body. The main function of the blood is the transport of oxygen to different parts of the body. It conveys nutritive substances and transports hormones, antibodies and enzymes. Blood maintains body temperature and removes toxins from the body. The blood is composed of Plasma, Erythrocytes (red blood cells), Leucocytes (white blood cells) and platelets.

Erythrocytes

Erythrocytes are present in the largest number in the blood. There are around 4.6 million erythrocytes per mm cube. Erythrocytes are devoid of a nucleus. It has a biconcave shape. The red cells are rich in Hemoglobin. Hemoglobin is a protein that binds to oxygen. They have a life span of 120 days.

Functions of erythrocytes

Erythrocytes have a specific shape and size, which is ideally suited to perform the function of ‘carrier of gases’. They possess distinct properties of biconcavity and reversible deformability. The flattened and biconcave shape provides a surface area most favorable for diffusion in and out of the cell. Reversible deformability enables the red blood cells to change their shape and squeeze through the microcirculation. The red blood cells have a prosthetic group and the active component of this group is Haem. Haem depends on the presence of Iron and it combines with Haemoglobin to form Oxyhaemoglobin. Oxygen combines with the haemoglobin in the blood as it passes through the lung capillaries. Oxyhaemoglobin returns to the heart through the pulmonary vein and enters the systemic circulation through the aorta.

Erythrocytes are eventually broken down into blood pigments namely Bilirubin and Biliverdin and Iron, in the spleen. These substances are then transported to the liver, by the blood. In the liver, Iron is re-cycled for use by other erythrocytes. The blood pigments form bile salts that help in digestion of fats.

The relative amounts of cholesterol and phospholids are responsible for the fluid properties of the erythrocyte membrane. Alteration in the membrane cholesterol-phospholipid ratio results in abnormal red blood cells with reduced life span.

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