This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Monocytes remains in the circulation for: March 2005 
Select and explain. 
A. 1-3 days, B. 24 hours, C. 12 hours, D. 6 hours
A: 1-3 days
Answer: A: 1-3 days 
Explanation: Ans. A: 1-3 daysMonocytes enter the circulation from the bone marrow and remains in circulation for about 72 hours. They then enter the tissues and become tissue macrophages. The tissue macrophages include Kupffer cells of liver, pulmonary alveolar macrophages and microglia in the brain