Question

Use the drop-down menus to determine whether the following barriers are physical, chemical, or biological.


lysozyme

skin

phagocytes

Langerhans cells

acid and oil secretions

sneezing or coughing

Answer 1

- Lysozyme — Chemical barrier (antimicrobial enzyme in tears, saliva, mucus)
- Skin — Physical barrier (intact epithelium blocks entry)
- Phagocytes — Biological barrier (cells that ingest and destroy microbes)
- Langerhans cells — Biological barrier (skin dendritic cells that recognize and present antigens)
- Acid and oil secretions — Chemical barrier (low pH and antimicrobial lipids inhibit microbes)
- Sneezing or coughing — Physical barrier (mechanical removal of pathogens from airways)