Question

Identify how the physical barriers of the immune system protect the body against pathogens. Check all that apply.

your nose produces oil to keep pathogens from entering the body through your nose

skin contains tightly packed cells

skin is tough, flexible, and waterproof

you cough when a pathogen enters your mouth

you sneeze when a pathogen enters your nose

Answer 1

Correct answers:
- skin contains tightly packed cells
- skin is tough, flexible, and waterproof
- you cough when a pathogen enters your mouth
- you sneeze when a pathogen enters your nose

Why: The skin’s tightly packed, keratinized cells form a physical barrier that is tough and water‑resistant, preventing pathogen entry. Coughing and sneezing are reflexes that expel irritants and microbes from the airways. The nose does not primarily produce oil to block pathogens — nasal passages produce mucus (and have hairs and cilia) to trap and remove microbes.