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

A 19-year-old female has just been extricated from a car accident and has several abrasions on her skin. Which of the following best describes the role of her skin in the body's first-line defenses?

The skin increases blood flow to remove toxins from the body.

The skin releases histamine to attract white blood cells to the site of injury.

The skin produces antibodies to neutralize invading microbes.

The skin acts as a physical barrier to prevent the entry of pathogens.

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Verified step by step guidance

Step 1: Understand the concept of the body's first-line defenses. The first-line defenses are physical and chemical barriers that prevent pathogens from entering the body. These include the skin, mucous membranes, and secretions like sweat and saliva.

Step 2: Analyze the role of the skin in the immune system. The skin acts as a physical barrier, preventing the entry of pathogens. It is composed of multiple layers, including the epidermis, which contains keratinized cells that are tough and resistant to microbial invasion.

Step 3: Evaluate the incorrect options. The skin does not increase blood flow to remove toxins (this is a function of the circulatory system during inflammation). It does not release histamine (this is done by mast cells during an immune response). The skin does not produce antibodies (antibodies are produced by B lymphocytes).

Step 4: Focus on the correct answer. The skin acts as a physical barrier to prevent the entry of pathogens. This is its primary role in the body's first-line defenses, supported by its structure and secretions like sebum, which have antimicrobial properties.

Step 5: Relate this to the scenario. In the case of abrasions, the physical barrier of the skin is compromised, increasing the risk of pathogen entry. This highlights the importance of the skin in maintaining the body's defenses against infection.