Final answer:
Epithelial membranes are either classified as simple if they are composed of a single layer of cells, or stratified if they consist of multiple layers. Simple epithelia are associated with absorption and filtration, while stratified epithelia protect against wear and tear.
Step-by-step explanation:
Epithelial membranes that are composed of two or more layers are considered stratified, while membranes that are a single layer of cells are simple. This classification is based on the number of cell layers that form the epithelial tissue. Simple epithelia, which are organized as a single layer of cells, are typically found where absorption and filtration occur and provide a barrier against pathogens. Stratified epithelia, with multiple layers of cells, are adapted to protect against physical and chemical wear and tear. Stratified epithelial tissues are thus commonly found in areas subjected to friction or stress, such as the skin's outer layer.