White Blood Cells | Biology for GCSE/IGCSE - Year 11 PDF Download

Lymphocytes & Phagocytes: Extended

• White Blood Cells and Immune Defense: White blood cells (leukocytes) play a crucial role in the body’s immune system, protecting against infections caused by pathogenic microorganisms such as bacteria, viruses, fungi, and parasites.
• Types of White Blood Cells:
  • Phagocytes: These cells, including neutrophils and macrophages, are responsible for ingesting and destroying pathogens. They do this through a process called phagocytosis, where they engulf the microorganisms and break them down using enzymes.
  • Lymphocytes: This group includes B cells and T cells, which are essential for the adaptive immune response. B cells produce antibodies that specifically target pathogens, while T cells help directly kill infected cells or assist in regulating other immune responses.

Phagocytes

• Engulfing and Digesting Pathogens: Phagocytes perform phagocytosis by engulfing and breaking down pathogens.
• Detection of Pathogens: Phagocytes have sensitive cell surface membranes that can detect chemicals released by pathogenic cells.
• Engulfment and Digestion: Upon encountering a pathogen, phagocytes engulf it and release digestive enzymes to break it down.
• Microscopic Identification: Phagocytes can be identified under a microscope by their multi-lobed nucleus and granular cytoplasm.

Lymphocytes

• Antibody and Antitoxin Production: Lymphocytes produce antibodies to destroy pathogens and antitoxins to neutralize toxins released by pathogens.
• Microscopic Identification: Lymphocytes can be recognized under a microscope by their large, round nucleus, which occupies most of the cell, and their clear, non-granular cytoplasm.