Physiology of dinosaurs and that this was a feature they shared with birds. In 2007 Oliver Wings reviewed references to gastroliths in scientific literature and found considerable confusion, starting with the lack of an agreed and objective definition of "gastrolith". He found that swallowed hard stones or grit can assist digestion in birds that mainly feed on grain but may not be essential—and that birds that eat insects in summer and grain in winter usually get rid of the stones and grit in summer. Gastroliths have often been described as important for sauropod dinosaurs, whose diet of vegetation required very thorough digestion, but
Extracellular digestion initial components of the gastrointestinal tract are the mouth and the pharynx, which is the common passage of the oral and nasal cavities. The pharynx leads to the esophagus, a muscular tube that delivers food to the stomach, where some preliminary digestion occurs; here, the digestion is extracellular. From the stomach, food passes to the small intestine, where a battery of digestive enzymes continue the digestive process. The products of digestion are absorbed across the wall of the intestine into the bloodstream. What remains is emptied into the large intestine, where some of the remaining water and minerals are absorbed;