Final answer:
The skin uses a physical barrier and secretes antimicrobial substances to protect against diseases caused by organisms.
Step-by-step explanation:
The mechanism that the skin uses to protect against diseases caused by organisms is Physical barrier and secretion of antimicrobial substances. Before any immune factors are triggered, the skin acts as a continuous, impassable barrier to potentially infectious pathogens. It also secretes antimicrobial substances that can kill or inactivate pathogens on the skin. Additionally, beneficial microorganisms that coexist on the skin compete with invading pathogens, preventing infection.