AAMA CMA Practice Question

The correct answer is "Intact skin acts as a physical barrier to prevent the entry of pathogens." The body's first line of defense consists of physical and chemical barriers that prevent pathogens from entering the body. Intact skin is the largest organ and the body's primary physical barrier against the external environment. While mucus in the respiratory tract and stomach acid are also crucial components of the first line of defense, skin represents the most extensive and significant initial barrier. Antibodies are part of the third line of defense, the adaptive immune response, which is a specific response to pathogens that have already entered the body.