The leucocyte on the left is a monocyte. The two leukocytes on the right are neutrophils.
Monocytes are components of the reticuliendothelial system. They mature into tissue macrophages.
- Shape: They are oval in shape and may also appear amoeboid.
- Size: The size ranges from 14-20µm in size. This is about two to three times the diameter of an erythrocytes.
- Nucleus: Classically the monocyte nucleus is described and kidney or bean shaped. It may take other shapes including horse/shoe, oval and folded.
- Cytoplasm: The cytoplasm is blue grey with fine lilac granules.
Neutrophils or polymorphonuclear neutrophils are granulocytes. They get their name from the fact that their cytoplasm has prominent granules. Neutrophils are so called because they have neutral (pink) staining granules against basophils (blue) and eosinophilic (brick red) granules. They are the most common cells on a peripheral smear.
- Size: The neutrophil is about 12-15μm in size. This is about slightly bigger than an RBC to twice the size of the RBC.
- Shape: neutrophils that have not been activated are round. Activated neutrophils become amoeboid.
- Nucleus: The nucleus has lobes. The number of lobes increase with age of the neutrophil. Finding more than five lobes is exceptional and needs investigation for megaloblastic anaemia or myelodysplasia.
- Cytoplasm: The cytoplasm has pink granules.