Final answer:
The body's first line of defense includes physical and chemical barriers like the skin, tears, and stomach acid to prevent pathogens from entering. Inflammation and white blood cells are activated if pathogens breach these barriers.
Step-by-step explanation:
Your body's first line of defense includes the skin and other barriers, such as tears, mucus, stomach acid, urine flow, and friendly bacteria. These barriers physically and chemically prevent most pathogens from entering the body. If pathogens breach these barriers, inflammation occurs, creating a physical barrier against the spread of infection and repairing tissue damage. Additionally, the complement system and various types of white blood cells are activated to phagocytize pathogens and trigger an immune response.