Immune System: A Constant Battle Against Pathogens

Introduction

• Our bodies are constantly fighting bacteria such as staph, strep, and E. coli.
• Immune system: a defense system not tied to specific organs but involves various tissue groups and cells.
• Functions to defend against infections in a germ-filled world.

First Line of Defense: Innate (Nonspecific) Immune System

• External Barriers
  • Skin: Acts as a physical wall like a fortress against microorganisms.
  • Mucous Membranes: Line cavities opening to the outside, providing a barrier and containing chemical defenses.
• Chemical Defenses
  • Stomach Acid: Destroys ingested pathogens.
  • Mucus: Traps pathogens in respiratory passages.
  • Enzymes: Present in saliva and eye fluid to fight bacteria.
  • Defensins: Peptides on skin to prevent bacterial and fungal growth.

Second Line of Defense: Internal Innate Defenses

• Phagocytes: Cells that consume pathogens.
  • Neutrophils: Most abundant, self-destruct after consuming pathogens, forming pus.
  • Macrophages: Larger, derived from monocytes, can repeatedly consume pathogens.
• Natural Killer (NK) Cells
  • Target infected or cancerous cells by inducing apoptosis (cell death).
• Inflammatory Response
  • Mast Cells & Histamine: Create vasodilation, heat, and redness, increasing blood flow and repair.
  • Increased Permeability: Causes swelling, aids in forming clots and scabs.
  • Phagocyte Attraction: Inflammation draws phagocytes to destroy pathogens.

Fever as a Defense Mechanism

• Pyrogens: Chemicals released to induce fever, enhancing cell metabolism and inhibiting bacterial growth.

Conclusion

• The innate immune system includes barriers, phagocytes, and inflammatory responses to fight infections.
• Adaptive immune defenses are called if innate responses are insufficient.

Acknowledgments

• Credits to contributors and production teams involved in creating educational content.