Erythrocytes: Morphology, Functions, RBC Counting, and Indices
Erythrocytes, also known as red blood cells (RBCs), are the most abundant cells in the blood, comprising approximately 40-45% of the total blood volume. They are responsible for the transportation of oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs. In this blog post, we will discuss the morphology of RBCs in health and disease, their functions, RBC counting, diluting fluids used, and erythrocyte indices.

Morphology of RBC in Health and Disease
In a healthy individual, RBCs are biconcave discs, approximately 7.5 micrometers in diameter, with a thin central pallor. However, in certain diseases such as sickle cell anemia and thalassemia, the shape of RBCs can be abnormal, leading to various complications. In sickle cell anemia, RBCs are crescent-shaped, while in thalassemia, they can be microcytic and hypochromic. The morphology of RBCs can provide valuable information for the diagnosis and monitoring of various blood disorders.
Functions of RBC
The primary function of RBCs is to transport oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs. This function is facilitated by the presence of hemoglobin, a protein that binds oxygen and carbon dioxide. Additionally, RBCs play a role in maintaining the pH balance of the blood.
RBC Counting and Diluting Fluids Used
RBC counting is an essential component of a complete blood count (CBC), a routine blood test that measures various blood components. To perform an RBC count, a diluting fluid is added to the blood sample, which helps to reduce the number of cells and make them easier to count. The most commonly used diluting fluids for RBC counting are isotonic saline, Hayem's fluid, and Turk's fluid. The choice of diluting fluid depends on the laboratory's preference and the type of blood sample being analyzed.
Erythrocyte Indices
Erythrocyte indices are derived from RBC counting and provide information on the size, shape, and hemoglobin content of RBCs. The three main indices are mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). MCV measures the average size of RBCs, MCH measures the average amount of hemoglobin in RBCs, and MCHC measures the concentration of hemoglobin in RBCs. These indices are useful for the diagnosis and monitoring of various blood disorders.
Frequently Asked Questions (FAQs)
Q: What is the normal range for RBC count?
A: The normal range for RBC count varies between men and women. In men, the range is typically 4.5-5.5 million cells/µL, while in women, it is 4.0-5.0 million cells/µL.
Q: What is the difference between MCV and MCHC?
A: MCV measures the average size of RBCs, while MCHC measures the concentration of hemoglobin in RBCs.
Q: What is the role of RBCs in acid-base balance?
A: RBCs play a role in maintaining the pH balance of the blood by acting as a buffer and helping to prevent excessive acid or base buildup.