Gastrointestinal tract -- layers, blood vessels, lymphatic vessels, nerves, suspensory folds, esophagus, stomach, histological organization of the stomach, cytology of gastric epithelial cells, gastrointestinal endocrine cells, small intestine, histological organization of the small intestine, cytology of the small intestine epithelium, regional differences, immune defense mechanisms, large intestine, histological organization of large intestine, cytology of the large intestinal epithelium, cetaceum and vermiform appendix, rectum and anus, epithelial replacements in the stomach, small intestine, and the large intestine, implications of epithelial removal.