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1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

21. The Immune System

Physical Barriers in First-Line Defenses: Skin

Anatomy & Physiology

21. The Immune System

Physical Barriers in First-Line Defenses: Skin

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Multiple Choice

Which of the following is not a physical barrier against infection?

Skin

Stomach acid

Mucous membranes

Tears

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Verified step by step guidance

Understand the concept of physical barriers in the immune system. Physical barriers are the first line of defense against pathogens and include structures that physically block or trap pathogens.

Identify the common physical barriers against infection. These include the skin, mucous membranes, and tears, which all serve to prevent pathogens from entering the body.

Recognize the function of the skin as a physical barrier. The skin acts as a protective layer, preventing the entry of pathogens through its tough outer surface.

Examine the role of mucous membranes. These membranes line various cavities in the body and secrete mucus, which traps pathogens and prevents them from entering further into the body.

Consider the function of tears. Tears help to wash away pathogens from the eyes, providing a physical barrier through the flushing action and the presence of antimicrobial substances.