tg Background information digestive system A series of hollow organs joined in a long twisting tube from the mouth to the anus. Inside this tube is a lining called the mucosa. In the mouth. stomach. and small intestine. the mucosa contains tiny glands that produce juices to help digest food.digestive system A series of hollow organs joined in a long, twisting tube from the mouth to the anus. Inside this tube is a lining called the mucosa. In the mouth, stomach, and small intestine, the mucosa contains tiny glands that produce juices to help digest food. . Background information