Granulocytes (including eosinophils) are distinguished from the other category of leucocytes, called agranulocytes, because granulocytes contain chemical-filled cytoplasmic vesicles called "granules".
- 2-4% of all white blood cells are eosinophils.
- Eosinophils are 10-12 um in diameter, have nuclei that have 2-3 lobes, and cytoplasm that includes large red-orange granules.
Eosinophils combat the effects of histamine in allergic reactions, phagocytize antigen-antibody complexes, and destroy certain parasitic worms. An increased (higher than usual) percentage of eosinophils in the blood may indicate parasitic infection somewhere in the body.
Phagocytosis is the engulfment and digestion of bacteria and other antigens by phagocytes, as shown:
For more information about other components (sometimes called the 'constituents') of blood, see the page about the structure and functions of blood. This may interest students of holistic massage, reflexology, beauty therapies, or health-related courses.