The present study aimed to compare the epithelium tissue of mucosa layer of gastrointestinal tract in three types of lower vertebrates: Scyliorhinus canicula, Sparus aurata, Salamandra infraimmaculata. The results of the histological and comparative study showed that the majority of digestion system parts were lined with simple epithelium tissue while others were lined by pseudostratified epithelium tissue. Goblet cells were distributed in all studied parts of digestion systems with density in some locations. Esophagus was characterized by ciliated epithelium tissue, and the tubular glands were presents in the stomach mucosa. Concerning the Lumina properia, it was visible in all digestive system parts with some differences according to the animal species studied.