Final answer:
The nurse would explain that the body's first barrier is the skin, which acts as a mechanical barrier to physically prevent pathogens from entering the body.
Step-by-step explanation:
When describing a person's barriers of defense, the nurse would explain that the body's first barrier is the skin. The skin acts as a mechanical barrier that physically blocks pathogens from entering the body. It is the most important and primary line of defense we have against external threats coming into contact with our body. The outer layer of the skin, the epidermis, is tough and constitutes a tough barrier that pathogens find very difficult to penetrate. Due to the presence of dead cells that are continually being shed, as well as sweat and other secretions that can lower the pH and wash microbes away, the skin is an effective way to prevent infections before they can start. The innate immune system includes this first line of defense, which is always at work to shield us from a broad range of pathogenic microbes.