Human digestive system a bolus which can be swallowed down the esophagus to enter the stomach. Here it is mixed with gastric acid until it passes into the duodenum where it is mixed with a number of enzymes produced by the pancreas. Saliva also contains a catalytic enzyme called amylase which starts to act on food in the mouth. Another digestive enzyme called lingual lipase is secreted by some of the lingual papillae on the tongue and also from serous glands in the main salivary glands. Digestion is helped by the chewing of food carried out by the muscles of mastication, by the
Development of the digestive system a membranous sac attached to the embryo, which provides nutrients and functions as the circulatory system of the very early embryo. The lateral body wall folds, pulling the amnion in with it so that the amnion surrounds the embryo and extends over the connecting stalk, which becomes the umbilical cord, which connects the fetus with the placenta. If the ventral body wall fails to close, ventral body wall defects can result, such as ectopia cordis, a congenital malformation in which the heart is abnormally located outside the thorax. Another defect is gastroschisis, a congenital defect in the anterior abdominal wall