WBCs or also known as Leucocytes are the colorless cells of the Blood. These cells do not contain Haemoglobin and thus are colorless. They do not have a fixed shape which enables them to move out of the capillaries by a process called Diapedesis.
The number of WBCs in the blood ranges from 6000-9000/mm3. An increase in number of WBCs is called Leucocytosis while decrease in its number is called Leucopenia.
The WBCs are divided into two groups on the basis of presence or absence of cytoplasmic granules (lysosomes containing different types of enzymes) i.e. Agranulocytes and Granulocytes.
1. AGranulocytes
These are the WBCs that do not contain cytoplasmic granules i.e. are agranular.
a. lymphocytes
Size- 7-8 μm (small lymphocytes) and 12-15 μm (large lymphocytes)
Formation- Formed by Lymphoblasts in the lymphatic tissues and bone marrow
Nucleus- Round
Functions- Synthesis of antibodies
DLC- 20-30%
Types- T-cells and B-cells
B. MONOCYTES
Size- 15-20 μm (Largest WBCs)
Formation- Formed by Monoblasts in the bone marrow and connective tissue
Nucleus- Kidney shaped
Functions- Phagocytosis
DLC- 4-8%
2. GRANULOCYTES
These are the WBCs that contain cytoplasmic granules. The formation of these cells occurs from the Myeloblasts.
A. Eosinophils
Size- 10-15 μm
Nucleus- Bilobed nucleus
Staining- Takes up acidic stains (also called Acidophils)
Functions- Produces antitoxins against allergens
DLC- 1-4%
B. BASOPHILS
Size- 10-15 μm
Nucleus- S shaped nucleus
Staining- Takes up basic stains like methylene blue
Functions- Produces Heparin and Histamines
DLC- 0-1% (least in number)
C. Neutrophils
Size- 10-14 μm
Nucleus- 2-7 lobed nucleus
Staining- Takes up neutral stains like neutral red
Functions- Phagocytosis
DLC- 60-65% (maximum in number)
