MCQ Detailed View

Red blood cells (RBCs), also called erythrocytes, are the most abundant type of blood cells in the human body. Their main function is to transport oxygen from the lungs to body tissues and carry carbon dioxide back to the lungs for exhalation. RBCs are produced in the bone marrow and have a lifespan of around 120 days.

In a normal adult human, the total number of red blood cells is approximately 30 trillion. Each microliter of blood contains roughly 4.5 to 5.5 million RBCs, and since the human body has about 5 liters of blood, the total number reaches around 30 trillion cells. This number can vary slightly depending on age, sex, health conditions, and environmental factors such as living at high altitudes.

RBCs are biconcave and disc-shaped, which increases their surface area and facilitates efficient gas exchange. They lack a nucleus, leaving more room for hemoglobin, the oxygen-binding protein essential for transporting oxygen. Hemoglobin binds oxygen in the lungs and releases it in the tissues, maintaining proper cellular function and energy production.

Other options in the question are less accurate:

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  15 trillion and 20 trillion are underestimations for an average adult.

  
  


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  25 trillion is slightly lower than the more widely accepted approximation.

  
  

Monitoring RBC count is important in medicine because abnormal RBC levels indicate health issues. A low RBC count can cause anemia, leading to fatigue and weakness, while a high RBC count (polycythemia) can increase the risk of blood clots and cardiovascular complications.

In summary, the correct answer is 30 trillion, representing the approximate total number of red blood cells in a normal human body. This knowledge is fundamental in biology, physiology, and medical sciences, as it helps understand oxygen transport, overall health, and blood-related conditions.