Question

Originating in bone marrow, circulating in blood for $1-2$ days migrating to connective tissue and forming macrophages is a characteristic of ______________.

• A. Monocytes
• B. Basophils
• C. Eosinophils
• D. Lymphocytes

Answer 1

The correct option is A Monocytes

Monocytes originate in the bone marrow from pluripotent stem cells; their direct precursor cell is the promonocyte that derives from the monoblast. After monocytes are formed by division of promonocytes, they remain only a very short time (less than a day) in the bone marrow compartment. When monocytes enter the circulation they are divided over a circulating pool and a marginating pool, each comprising about 50% of the monocytes present in the blood vessels. Monocytes stay for a relatively long time in the circulation, the half-life being 71 h (humans). Then they leave this compartment randomly by a process called diapedesis(Diapedesis is defined in immunology as the outward passage of cells through the intact vessel wall) and migrate to tissues and body cavities where they differentiate into macrophages.

So, the correct answer is 'Monocytes'.