Multiple Choice
Saliva and lacrimal fluids contain which enzyme that destroys bacteria?
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21. The Immune System
Physical Barriers in First-Line Defenses: Mucous Membrane
Problem 5
Textbook Question
Which of the following make up the body's first line of defense?
a. Surface barriers
b. Cells and proteins of adaptive immunity
c. Cells and proteins of innate immunity
d. All of the above
Verified step by step guidance1
Understand the concept of the body's first line of defense: The first line of defense refers to physical and chemical barriers that prevent pathogens from entering the body. These are nonspecific defenses and are part of innate immunity.
Identify surface barriers as part of the first line of defense: Surface barriers include the skin and mucous membranes, which act as physical barriers to block pathogen entry. Additionally, secretions like mucus, sweat, and tears contain antimicrobial substances.
Differentiate between innate and adaptive immunity: Innate immunity is the body's immediate, nonspecific response to pathogens, while adaptive immunity involves a specific response and memory of pathogens. The first line of defense is part of innate immunity, not adaptive immunity.
Evaluate the options provided: Surface barriers (option a) are part of the first line of defense. Cells and proteins of innate immunity (option c) are part of the second line of defense, which responds after pathogens bypass the first line. Adaptive immunity (option b) is the third line of defense and is not part of the first line.
Conclude which option is correct: Based on the explanation, the correct answer is surface barriers (option a), as they exclusively make up the body's first line of defense.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
First Line of Defense
The first line of defense refers to the body's initial protective mechanisms against pathogens. This includes physical and chemical barriers such as skin, mucous membranes, and secretions like saliva and tears, which prevent the entry of harmful microorganisms.
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Innate Immunity
Innate immunity is the body's immediate and non-specific response to pathogens. It includes various cells and proteins, such as phagocytes and natural killer cells, that act quickly to eliminate invaders and is considered a crucial part of the first line of defense.
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Adaptive Immunity
Adaptive immunity is a specific immune response that develops over time, involving lymphocytes such as B cells and T cells. While it is essential for long-term protection and memory against specific pathogens, it is not part of the first line of defense, which acts more rapidly.
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