Final answer:
Monocytes are agranulocytes that make up 2-8% of leukocytes in blood, originating from myeloid stem cells, and differentiate into macrophages to aid in immune responses.
Step-by-step explanation:
Monocytes are a type of white blood cells originating from myeloid stem cells. They account for 2-8 percent of the total leukocyte (white blood cell) count in the blood. Monocytes are characterized by their large size, ranging from 12-20 µm, and their distinct indented or horseshoe-shaped nuclei. In terms of their granularity, monocytes are classified as agranulocytes, which means they have fewer and less obvious granules compared to granular leukocytes. Once monocytes migrate out of the bloodstream and into body tissues, they differentiate into macrophages. These macrophages are essential for phagocytizing debris, foreign pathogens, and worn-out cells. Furthermore, they release antimicrobial defensins and chemotactic chemicals that attract other leukocytes to the site of infection, playing a significant role in the immune response.