The document summarizes the structure and function of the digestive system. It begins with an overview of the main functions and divisions. It then describes in detail the layers, cell types, and glands found in the oral cavity, esophagus, stomach, small intestine and their roles in digestion. The mucosa contains the epithelial lining and glands that secrete enzymes and mucus. Underlying layers include the submucosa and muscularis for support and movement. Together these components mechanically and chemically break down food into absorbable nutrients.