Overview
This lecture discusses the physical and chemical barriers that protect the body from disease-causing organisms (pathogens), and provides examples of each barrier.
Chemical Barriers
- Stomach acid (hydrochloric acid) destroys pathogens in food by denaturing their enzymes due to its low pH.
- Mucus is produced by goblet cells in body linings and traps pathogens.
- Mucus, swept along by cilia (hairlike structures), moves trapped pathogens out of the body.
Mechanical Barriers
- Skin acts as a physical shield preventing pathogen entry, with a tough outer layer made of keratin.
- Blood clotting acts as a repair mechanism, sealing breaks in the skin to maintain the barrier.
- Nostril hairs trap pathogens before they can enter the respiratory system.
Key Terms & Definitions
- Pathogen — A disease-causing organism, such as a virus or bacteria.
- Stomach acid — Hydrochloric acid in the stomach with low pH that destroys pathogens.
- Mucus — A sticky substance produced by goblet cells that traps pathogens.
- Goblet cells — Cells that produce mucus in various linings of the body.
- Cilia — Hairlike structures that move mucus and trapped pathogens.
- Keratin — A tough protein forming the outer layer of skin.
- Blood clot — A mechanism to seal cuts in the skin, maintaining the barrier.
Action Items / Next Steps
- Review examples of chemical and mechanical barriers for exam preparation.
- Practice explaining how stomach acid protects against disease, using specific details.