Question

Describe five types of leucocytes, with the help of diagrams. Add a note on their functions.

Answer 1

Leucocytes are colourless, nucleated, amoeboid and phagocytic cells.
Leucocytes are of two types: Granulocytes and Agranulocytes.

i. Granulocytes: They are produced in red bone marrow and contain large sized granules in the cytoplasm.
Granulocytes are of three types:

1. Neutrophils (neutro = neutral, philic = affinity)
   They constitute about 70% of total WBCs.
   Nucleus is multilobed containing 3 to 5 lobes.
   The granules in cytoplasm of these cells take up neutral stain. 
   Functions: These are chief phagocytic cells.
   They protect the body against invasion of bacteria.
   Dead neutrophils along with damaged tissue are removed from the body in the form of pus.
   
2. Eosinophils (acidophils):
   They constitute about 3% of total WBCs.
   The nucleus is bilobed.
   The granules in the cytoplasm of these cells take up acidic stain. 
   Functions:
   They are non-phagocytic and their number increases during allergic reactions. They show anti-histamine property.
   
3. Basophils:
   They are the smallest white blood cells which constitute about 0.5% of the total WBCs.
   They show twisted nucleus (‘S’ or comma shaped).
   The granules in the cytoplasm of these cells take up basic stain. 
   Functions:
   They are non-phagocytic.
   They secrete heparin, histamine, thus play an important role in local anticoagulation and formation of ground substance.
   

ii. Agranulocytes: They are produced in spleen and do not contain  granules in the cytoplasm.
Agranulocytes are of two types: 

1. Lymphocytes: They form 30% of total WBCs.
   Nucleus is large, spherical and surrounded by thin layer of cytoplasm.
   Functions: They produce antibodies and opsonins to neutralize the harmful effects of foreign matter and their toxins. 
   
2. Monocytes: They are the largest leucocytes and constitute 1 to 3% of total WBC. They have large amount of cytoplasm and kidney shaped nucleus.
   Functions: They are phagocytic in action. They engulf foreign particles. e.g. bacteria.
   They also remove the damaged and dead cells, hence are  referred to as scavengers