A mucous membrane is a protective layer of tissue that lines various cavities and organs in the body, such as the nose, mouth, and digestive tract. This membrane produces a thick fluid called mucus, which helps keep these areas moist and traps dust, germs, and other particles, preventing them from entering the body. Mucous membranes play a crucial role in our immune system by acting as a barrier against infections. They also help with functions like digestion and respiration by facilitating the movement of food and air. Overall, these membranes are essential for maintaining our health and well-being.