Mucosa is the thin layer of tissue that covers the inner surfaces of the body including body cavities and hollow organs. The surface of the eye is also covered by mucosa. Mucosal creates a barrier between the outside world and the inside of the body. If the mucosa becomes damages or lost, infectious agents such as bacteria or fungus can get into the body.
While all of these surfaces are called mucosa, they are not all made up of the same types of cells. For example, the mucosa lining the inside of the mouth is made up of specialized cells called squamous cells while the inside of the colon is made up of specialized cells that connect together to form glands.
Many types of cancer start from the cells in the mucosa. The group of cancers that start from cells in the mucosa are called carcinomas. Carcinomas that start from mucosa made up of squamous cells are called squamous cell carcinoma while those that start from mucosa made up of glands cells are called adenocarcinoma.