Human Body Defense System

Overview

• The defense system protects against pathogens.
• Divided into:
  • Physical and Chemical Barriers: Prevent pathogen entry.
  • Immune System: Destroys pathogens that enter.

Physical and Chemical Barriers

Skin

• Acts as a physical barrier.
• Secretes oils and antimicrobial substances.
• Pathogens can't penetrate intact skin.

Nasal Defense

• Hairs and Mucus in the nose trap pathogens/particles.

Respiratory Tract

• Trachea and Bronchi:
  • Lined with mucus to trap particles.
  • Cilia move mucus to the throat for swallowing.

Stomach

• Produces Hydrochloric Acid:
  • Lowers pH to 2, killing pathogens.

Immune System

White Blood Cells

• Continuously patrol the body.
• Three key functions:
  1. Phagocytosis
     • White blood cells engulf and destroy pathogens.
  2. Antitoxin Production
     • Neutralize toxins produced by pathogens.
  3. Antibody Production
     • Antibodies bind to antigens (foreign substances).
     • Act as signals for white blood cells.
     • Antibodies are specific to particular antigens.

Antigens vs. Antibodies

• Antigens: Detected as foreign by the immune system (e.g., bacteria cell wall, virus protein).
• Antibodies: Created by white blood cells to target specific antigens.
  • Facilitate immune response by marking pathogens.

Immunity

• Memory Cells:
  • Remember specific antibodies required to fight specific pathogens.
  • Rapid antibody production on re-exposure to same pathogen.
  • Concept of being immune to a disease.

Additional Resources

• Cognito Website: Provides videos, questions, flashcards, exam questions, past papers.
• Progress tracking available.
• Free sign-up for additional study aids and resources.