Sample Answer

Blood’s formed elements, crucial for life, include red blood cells (RBCs) and white blood cells (WBCs).  

Red Blood Cells (Erythrocytes): These biconcave discs, devoid of a nucleus, are packed with hemoglobin, an iron-containing protein that transports oxygen. Their primary function is to deliver oxygen from the lungs to body tissues and carry carbon dioxide back.  

White Blood Cells (Leukocytes): These cells defend the body against pathogens and foreign substances. They are classified into:  

• Granulocytes:
  • Neutrophils: The most abundant, they phagocytize bacteria and debris.  
  • Eosinophils: Combat parasitic infections and allergic reactions.  
  • Basophils: Release histamine and other inflammatory mediators.  
• Agranulocytes:
  • Lymphocytes: Include T cells (cell-mediated immunity), B cells (antibody production), and natural killer cells (destroy infected cells).  
  • Monocytes: Differentiate into macrophages, which phagocytize pathogens and cellular debris.  

Blood Types:

Blood types are determined by the presence or absence of specific antigens (A and B) on the surface of RBCs.  

• Type A: Has A antigens and anti-B antibodies.
• Type B: Has B antigens and anti-A antibodies.