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

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 a physical barrier against pathogens in the first-line defenses of the skin?

Mucous membranes

Lymphocytes

Sebaceous glands

Epidermis

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Verified step by step guidance

Understand the concept of the body's first line of defense: The first line of defense includes physical and chemical barriers that are always ready and prepared to defend the body from infection. These barriers include the skin, mucous membranes, and secretions.

Identify the role of the epidermis: The epidermis is the outermost layer of the skin, which acts as a physical barrier to protect the body from pathogens, such as bacteria and viruses.

Differentiate between physical and chemical barriers: Physical barriers, like the epidermis, provide a tough outer layer that prevents pathogens from entering the body. Chemical barriers, such as secretions from sebaceous glands, can also protect by creating an environment hostile to pathogens.

Evaluate the options given: Mucous membranes are also a physical barrier but are not part of the skin. Lymphocytes are part of the immune response, not a physical barrier. Sebaceous glands produce sebum, which is a chemical barrier.

Conclude that the epidermis is the correct answer: Since the epidermis is the outermost layer of the skin and serves as a physical barrier, it is the correct answer to the question.