Mucosa is a type of tissue that lines various cavities and organs in the body, such as the mouth, nose, digestive tract, and respiratory system. It serves as a protective barrier and plays a crucial role in absorption and secretion. The mucosa is made up of epithelial cells and is often supported by a layer of connective tissue. This tissue is important for maintaining moisture and facilitating the movement of substances. In the digestive system, for example, the mucosa helps in the absorption of nutrients, while in the respiratory system, it traps dust and pathogens to keep the airways clear.