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

Introduction to First-Line Defenses

Anatomy & Physiology

21. The Immune System

Introduction to First-Line Defenses

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Multiple Choice

Which of the following provides a first line of defense against pathogens?

Antibodies

Skin

B cells

T cells

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Verified step by step guidance

Understand the concept of the body's defense mechanisms: The human body has multiple layers of defense against pathogens, which are organisms that can cause disease.

Identify the first line of defense: The first line of defense includes physical and chemical barriers that prevent pathogens from entering the body.

Recognize the role of the skin: The skin acts as a physical barrier, preventing the entry of pathogens. It is part of the innate immune system, which provides immediate defense.

Differentiate between the options: Antibodies, B cells, and T cells are part of the adaptive immune system, which is a later response to pathogens. They are not part of the first line of defense.

Conclude that the skin is the correct answer: Given its role as a physical barrier, the skin is the first line of defense against pathogens, unlike antibodies, B cells, and T cells, which are involved in later stages of immune response.