Final answer:
Epithelial membranes composed of multiple layers are classified as stratified, while those made up of a single layer are called simple. The number of layers in epithelial tissues varies based on their location and function in the body, providing differing degrees of protection.
Step-by-step explanation:
Epithelial membranes that are composed of 2 or more layers are considered stratified, while membranes that are a single layer of cells are simple. Epithelial tissues are crucial for protecting both the external and internal surfaces of the body. They serve as a barrier and are involved in absorption, filtration, excretion, secretion, and sensory reception.
The classification of epithelial tissues includes two main aspects: the number of cell layers and the shape of the cells. Simple epithelia consist of a single layer of cells where each cell extends from the basal lamina to the free surface. In distinct contrast, stratified epithelia are composed of multiple layers of cells, providing a greater degree of protection. Specialized forms like transitional epithelium are capable of stretching and are found in structures like the bladder.