What is the percentage of erythrocytes in a volume of blood:
The correct answer and explanation is:
Correct Answer: The percentage of erythrocytes (red blood cells) in a volume of blood is typically about 45%.
Explanation (Approx. 300 Words):
The percentage of erythrocytes in a volume of blood is measured by a test called the hematocrit. The hematocrit indicates the proportion of blood volume that is occupied by red blood cells (RBCs). On average, this value is around 45% in healthy adults, but it can vary slightly based on sex, age, and health status:
- Men: 40–54%
- Women: 36–48%
- Children: 35–45%
This means that in a typical blood sample, approximately 45% of the volume consists of erythrocytes, while the remaining 55% consists of plasma (the fluid portion), leukocytes (white blood cells), and platelets.
Role of Erythrocytes:
Erythrocytes are critical for transporting oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs. They contain hemoglobin, a protein that binds to oxygen and gives red blood cells their color.
Clinical Importance:
Knowing the hematocrit is essential in diagnosing and monitoring a variety of medical conditions:
- High hematocrit (>55%) may indicate dehydration, polycythemia vera (a bone marrow disorder), or adaptation to high altitudes.
- Low hematocrit (<35%) can suggest anemia, blood loss, or overhydration.
Hematocrit is usually measured as part of a Complete Blood Count (CBC) test. The sample is spun in a centrifuge, separating components by density, and the proportion of red cells is then measured.
Maintaining a normal hematocrit is vital because a low RBC percentage may impair oxygen delivery to tissues, while an abnormally high percentage may increase blood viscosity, raising the risk of clotting, stroke, or heart strain.