Summary
Defense against infectious diseases involves understanding how pathogens like bacteria, viruses, protozoa, and fungi cause diseases and how the body defends itself using barriers like skin and mucous membranes, blood clotting, and immune responses.
- Bacteria — Prokaryotes that divide by binary fission. Example: Cause food poisoning and cholera.
- Viruses — Acellular entities needing a host cell to reproduce. Example: Cause flu and HIV/AIDS.
- Protozoa — Simple parasites. Example: Cause malaria.
- Fungi — Eukaryotes that reproduce with spores. Example: Cause athlete's foot.
- Skin — Acts as a physical barrier to infection. Example: Secretes chemicals to inhibit microbial growth.
- Mucous Membranes — Protect internal structures by trapping pathogens. Example: Found in the trachea and urethra.
- Blood Clotting — Seals cuts to prevent pathogen entry. Example: Involves platelets and fibrin.
- Phagocytes — White blood cells that ingest pathogens. Example: Engulf pathogens through phagocytosis.
- Antibodies — Proteins produced by B lymphocytes specific to antigens. Example: Bind to unique antigens to neutralize them.
- Antibiotics — Drugs that target bacterial processes. Example: Ineffective against viruses.
Exam Tips
Key Definitions to Remember
- Pathogen
- Antigen
- Antibody
- Antibiotic
Common Confusions
- Difference between bacteria and viruses
- Why antibiotics don't work on viruses
Typical Exam Questions
- What is the role of skin in defense against pathogens? Acts as a physical barrier and secretes antimicrobial substances.
- How do phagocytes contribute to immunity? They ingest and destroy pathogens through phagocytosis.
- Why can't antibiotics treat viral infections? Viruses lack the structures and metabolic pathways targeted by antibiotics.
What Examiners Usually Test
- Understanding of pathogen types and examples
- Mechanisms of blood clotting
- Differences between specific and non-specific immunity
