Natural barriers of the body that protect against infections are known as what?

• A. The non-specific immune system
• B. The specific immune system
• C. The circulatory system
• D. The endocrine system

Answer: (A)

Natural barriers protect against infections by forming the first line of defense known as the non-specific, or innate, immune system. These barriers respond quickly to a wide range of pathogens in the same way and don’t require prior exposure. They include physical defenses like intact skin and mucous membranes that block entry, and chemical/biochemical defenses such as sweat, oil, tears, saliva, mucus, stomach acid, and beneficial normal flora that deter or suppress invaders. Because these responses aren’t tailored to a specific microbe and act immediately, they’re classified as non-specific. In contrast, the specific immune system is adaptive and targets particular pathogens with tailored responses and memory after exposure, while the circulatory and endocrine systems aren’t barriers themselves, though they support immune function.