Digestive system of gastropods species that have undergone de-torsion, however, the oesophagus may open into the anterior of the stomach, which is therefore reversed from the usual gastropod arrangement. In "Tarebia granifera" the brood pouch is above the oesophagus. There is available an extensive rostrum on the anterior part of the oesophagus in all carnivorous gastropods. Some basal gastropod clades have oesophageal gland. In most species, the stomach itself is a relatively simple sac, and is the main site of digestion. In many herbivores, however, the hind part of the oesophagus is enlarged to form a crop, which, in terrestrial pulmonates, may even replace
Human digestive system intestine. The mouth is the first part of the upper gastrointestinal tract and is equipped with several structures that begin the first processes of digestion. These include salivary glands, teeth and the tongue. The mouth consists of two regions; the vestibule and the oral cavity proper. The vestibule is the area between the teeth, lips and cheeks, and the rest is the oral cavity proper. Most of the oral cavity is lined with oral mucosa, a mucous membrane that produces a lubricating mucus, of which only a small amount is needed. Mucous membranes vary in structure in the different regions