Table of contents

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

First-Line Defenses: Chemical Barriers

Anatomy & Physiology

21. The Immune System

First-Line Defenses: Chemical Barriers

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Multiple Choice

Which of the following is NOT a chemical barrier against pathogens?

Skin

Lysozyme in saliva

Stomach acid

Sebum

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Verified step by step guidance

Understand the concept of chemical barriers: Chemical barriers are substances produced by the body that help prevent pathogens from entering or surviving in the body. They include enzymes, acids, and other antimicrobial substances.

Identify the options given: The options provided are Skin, Lysozyme in saliva, Stomach acid, and Sebum.

Recognize the role of each option: Lysozyme in saliva is an enzyme that breaks down bacterial cell walls, stomach acid is highly acidic and kills many pathogens, and sebum is an oily substance that can inhibit bacterial growth.

Consider the nature of skin: Skin is primarily a physical barrier, not a chemical one. It acts as a protective layer preventing pathogens from entering the body.

Determine which option does not fit the category of chemical barriers: Since skin is a physical barrier, it is not considered a chemical barrier against pathogens.