The slide shows an example of stratified squamous nonkeratinized epithelia from the esophagus. The surface cells of non-keratinized epithelia are living cells. Non-keratinized surfaces must be kept moist by bodily secretions to prevent them from drying out. They usually secrete mucus as an additional protective and lubricating layer that is why they are seen in the esophagus and in parts of the female reproductive system.