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Ch. 16 - Innate Immunity: Nonspecific Defenses of the Host
Chapter 12, Problem 16.1a

Identify at least one physical factor and one chemical factor that prevent microbes from entering the body through each of the following:
a. urinary system
b. genital system

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1
Identify the physical barriers in the urinary system: The flow of urine is a physical factor that helps to flush out microbes, preventing them from ascending into the urinary tract.
Identify the chemical barriers in the urinary system: Urine has a slightly acidic pH and contains urea, which can inhibit microbial growth.
Identify the physical barriers in the genital system: In females, the vaginal epithelium and mucus act as physical barriers to microbial entry.
Identify the chemical barriers in the genital system: The vaginal flora, particularly Lactobacillus species, produce lactic acid, maintaining an acidic environment that inhibits pathogen growth.
Consider how these factors work together: Both physical and chemical barriers in these systems work synergistically to prevent microbial colonization and infection.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Physical Barriers

Physical barriers are the first line of defense against microbial invasion. In the urinary system, the urethra's length and the flow of urine help flush out potential pathogens. Similarly, in the genital system, the presence of mucosal membranes and the external genitalia provide a physical barrier that limits microbial entry.
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Chemical Defenses

Chemical defenses involve substances produced by the body that inhibit microbial growth. In the urinary system, urine's acidic pH and the presence of antimicrobial peptides help prevent infections. In the genital system, secretions such as vaginal flora produce lactic acid, creating an acidic environment that deters harmful microbes.
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Microbial Flora

Microbial flora, or microbiota, are the beneficial microorganisms that reside in various body systems. In both the urinary and genital systems, these flora compete with pathogenic microbes for resources and space, thereby reducing the likelihood of infection. A healthy balance of these microorganisms is crucial for maintaining the integrity of these systems.
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