Multiple Choice
What is the most extensive physical barrier that prevents foreign substances from entering the body?
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21. The Immune System
Physical Barriers in First-Line Defenses: Skin
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Which of the following does not form part of the physical barriers in the first-line defenses of the skin?
A
Mucous membranes
B
Epidermis
C
Sebum
D
Keratin
Verified step by step guidance1
Understand the concept of physical barriers in the first-line defenses of the skin. These barriers are structures that physically block pathogens from entering the body.
Identify the components that typically make up the physical barriers. These include the epidermis and mucous membranes, which are structural layers that prevent pathogen entry.
Recognize that sebum is not a structural component but rather an oily secretion produced by sebaceous glands. It plays a role in chemical defense by creating an acidic environment on the skin surface.
Keratin is a protein found in the epidermis that provides strength and waterproofing, contributing to the physical barrier function of the skin.
Conclude that sebum, being a chemical secretion rather than a structural layer, does not form part of the physical barriers in the first-line defenses of the skin.
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