Human Body's Defense System

Overview

• The body's defense system protects against pathogens.
• Divided into physical/chemical barriers and the immune system.

Physical and Chemical Barriers

Skin

• Acts as a physical barrier.
• Secretes oils and antimicrobial substances to kill pathogens.

Nasal Defenses

• Hairs and Mucus: Trap pathogens and particles in the air.

Respiratory Tracts

• Trachea, Bronchi, and Bronchioles: Covered with mucus to trap particles.
• Cilia: Moves mucus to the throat.

Stomach

• Contains hydrochloric acid, lowering pH to about 2, killing most pathogens.

Immune System

White Blood Cells

• Patrol the body in blood and tissues.
• Functions:
  • Phagocytosis: Engulf and destroy pathogens.
  • Producing Antitoxins: Counteract toxins produced by pathogens.
  • Producing Antibodies:
    • Antibodies vs. Antigens: Key Terms
      • Antigens: Foreign substances detected by the immune system.
      • Antibodies: Proteins made by white blood cells to lock onto antigens.
    • Antibodies signal white blood cells to destroy pathogens.
    • Each antibody is specific to a particular antigen.
    • Memory function allows rapid response to previously encountered pathogens, creating immunity.

Conclusion

• The immune system helps defend against daily pathogen attacks.

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