1 Release of water, acids, enzymes, and buffers by the digestive tract and by the accessory organs into the lumen of the digestive tract. 2  Absorption. 3  Movement of small organic molecules, electrolytes, vitamins, and water across the digestive epithelium and into the blood and lymph.astrointestinal (GI) tract (also called alimentary canal or digestive tract). 1  The GI tract is a continuous tube running from the mouth to the anus. 2  It includes the following organs: 3  mouth. 4  pharynx. 5  esophagus. 6  stomach. 7  small intestine. 8  large intestine.