Mucous membranes are quite thin and fragile. How can such delicate tissue provide defense against microbial invaders?

The mucus is a physical trap that contains a variety of antimicrobial chemicals.
The mucus contains a variety of antimicrobial chemicals and molecules.
The mucus secreted by the mucous membrane physically traps microbes.
Both the mucus and the outer layer of cells are shed frequently.
The mucus physically traps microbes, contains a variety of antimicrobial chemicals, and is shed constantly, along with the outermost layer of cells.