Multiple Choice
Which of the following is a physical barrier against pathogens in the first-line defenses of the skin?
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21. The Immune System
Physical Barriers in First-Line Defenses: Skin
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Does the skin provide a diffusion barrier to all gases?
A
No, the skin allows only toxic gases to diffuse through.
B
No, the skin allows some gases like oxygen and carbon dioxide to diffuse through.
C
Yes, but only when the skin is dry.
D
Yes, the skin completely blocks all gases from diffusing through.
Verified step by step guidance1
Understand the structure of the skin: The skin is composed of multiple layers, including the epidermis, dermis, and subcutaneous tissue. The outermost layer, the epidermis, acts as a barrier to many substances.
Consider the properties of gases: Gases like oxygen and carbon dioxide are small and nonpolar, which allows them to diffuse through certain barriers more easily than larger or polar molecules.
Evaluate the permeability of the skin: While the skin is a barrier to many substances, it is not completely impermeable. Some gases can diffuse through the skin, particularly those that are small and nonpolar.
Recognize the physiological role of gas exchange: The skin does allow for some gas exchange, although it is not the primary site for this process. The lungs are the main organs responsible for gas exchange in the body.
Conclude with the correct understanding: The skin does not completely block all gases. It allows some gases, like oxygen and carbon dioxide, to diffuse through, although this is limited compared to the respiratory system.
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