MCQ Detailed View

White Blood Cells (WBCs), also known as leukocytes, are a crucial part of the human immune system. They protect the body against infections, bacteria, viruses, and other harmful microorganisms. While red blood cells are mainly responsible for carrying oxygen, white blood cells act as the defense soldiers of the body, constantly searching for pathogens to destroy.

The lifespan of white blood cells varies depending on their type, but on average, they live for 5 to 21 days. Some WBCs, like neutrophils, survive only a few hours to a few days, while others, such as certain lymphocytes, can live for several weeks or even months under specific conditions. However, the typical range for most WBCs in healthy human blood is between 5 and 21 days before they are naturally replaced.

White blood cells are produced in the bone marrow and then released into the bloodstream. Their production increases rapidly when the body encounters an infection or injury. Once their job of fighting harmful agents is complete, older WBCs die naturally and are removed from the body by the spleen and liver.

There are different types of WBCs, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each type plays a specific role in defending the body. For example:

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  Neutrophils quickly attack bacteria and fungi.

  
  


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  Lymphocytes help build long-term immunity.

  
  


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  Monocytes clean up dead cells and fight chronic infections.

  
  

Even though their lifespan is limited, the body constantly produces new white blood cells to maintain a strong immune defense. A healthy balance between production and natural death of WBCs is essential for overall health.

Thus, the correct answer is 5 – 21 days, as this is the typical lifespan range of most white blood cells circulating in the human body.