What constitutes the first line of resistance in the body?

• A. Inflammation and leukocyte actions
• B. Physical barriers like skin and mucous membranes
• C. Immunocyte activation and antibody production
• D. Cellular metabolism and repair mechanisms

Answer: (B)

The first line of resistance in the body consists of physical barriers such as the skin and mucous membranes. These structures play a crucial role in preventing pathogens and harmful substances from entering the body. The skin acts as a formidable external barrier, providing protection against physical damage and microbial invasion due to its multiple layers and associated sebaceous and sweat glands, which can excrete antibacterial substances.

Mucous membranes line various body cavities and also serve as a protective layer; they trap pathogens and particulate matter in mucus and contain antimicrobial properties. This combination of structural defenses offers an immediate response to pathogens trying to breach the body's entry points.

While inflammation, leukocyte actions, immunocyte activation, and repair mechanisms are all vital components of the immune response, they function primarily after the initial barrier is breached. Therefore, the skin and mucous membranes are foundational to the body's innate defense system.