Red Blood Cells | Formation and Function:

Introduction:

Red Blood Cells are otherwise called erythrocytes. Erythrocyte is derived from the Greek word erythros means ‘red’ and kytos means ‘hollow vessel’. Erythrocytes are circular biconcave nonnucleated discs with a diameter is about 7 microns. RBC is red due to the presence of hemoglobin. Hemoglobin is the protein used to carry oxygen and other essential nutrients.

Formation of Red Blood Cells:

All blood cells originate from pluripotent stem cells and undergo several developing stages before entering the blood.

Stages of Red Blood Cell formation:

Pluripotent stem cells:

Pluripotent stem cells can divide and differentiate into any type of three embryonic layers that can form specialized body cells or tissues. Three embryonic layers are endoderm, mesoderm, and ectoderm. Especially the mesoderm layer is responsible for the formation of blood cells.

Proerythroblast:

These are also called pronormoblast. Proerythroblasts are larger cells with basophilic, round nuclei, agranular, and have high nuclear-cytoplasmic ratios. Proerythroblasts are the earlier erythroid precursor and give rise to basophilic erythroblasts.

Basophilic erythroblast:

Basophilic erythroblasts are also known as basophilic normoblasts. These are formed by the mitotic cell division from proerythroblast. Basophilic erythroblasts are smaller than proerythroblasts, with more condensed chromatin and lower nuclear-cytoplasmic ratios. Basophilic erythroblasts form large amounts of ribosomes. In this stage, hemoglobin has been synthesized.

Reticulocyte:

Reticulocytes are the immature red blood cells produced from the bone marrow and released in the peripheral blood. These reticulocytes matured into RBCs within 1 to 2 days.

Erythrocyte:

Erythrocytes are matured red blood cells. It is the final stage of RBC production. It is red due to the presence of hemoglobin.

Normal range and life span of Red Blood Cells:

Red Blood Cell count:

• Male – 4.5 to 6.5 million/mm³
• Female– 4.5 to 5 million/mm³

Hemoglobin:

This is weight of hemoglobin in whole blood, measured in grams per 100ml.

• Male – 13 to 18 g/100ml
• Female – 11.5 to 16.5 g/100ml

Life span of Red Blood Cells:

The normal life span of Red Blood Cells is about 110 -120 days and the newborn has 60 to 90 days. After the end of their life span, they are engulfed by the macrophages.

Functions of Red Blood Cells:

Transportation of gases:

• RBC’s main function is to transport oxygen from the lungs to the whole body cells and tissues.
• It also excretes carbon dioxide from the body.

Transport essential nutrients:

Digested food was absorbed through the walls of the small intestine and the nutrients such as glucose, amino acids, and fatty acids were transported by blood bloodstream to various cells used as energy.

Determination of blood groups:

Red Blood Cells carry blood grouping antigens like A, B, O, etc. These are used to know about a person’s blood type and to prevent agglutination due to incompatible blood transfusion.