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 moistens and softens food, and along with the chewing action of the teeth, transforms the food into a smooth bolus. The bolus is further helped by the lubrication provided by the saliva in its passage from the mouth into the esophagus. Also of importance is the presence in saliva of the digestive enzymes amylase and lipase. Amylase starts to work on the starch in carbohydrates, breaking it down into the simple sugars of maltose and dextrose that can be further broken down in the small intestine. Saliva in the mouth can account for 30% of this initial starch digestion. Lipase