The ingested food is solid. It consists of complex insoluble organic substances. The conversion of complex insoluble food ingredients into simple absorbable form is called digestion.
The digestive system of frog starts from the mouth. Maxillary teeth are present on the upper jaw and there are no teeth on the lower jaw. Teeth are used to grasp the food and not for grinding the food. The frog has a sticky tongue. It is attached to the anterior end of the mouth cavity and the posterior end is free.
When the frog see its prey, it suddenly throws its tongue out of the mouth and the prey gets sticked to the sticky tongue and when it draws back the tongue the prey is brought to the buccal cavity.
From the mouth the food enters into the pharynx and then to the esophagus which opens into the stomach. The food is softened, broken down, and stored in the stomach. The anterior region of the stomach is called Cardiac end and the posterior region is called pyloric end.
The protein digestion starts from the stomach. The stomach leads into the small intestine. The first region of the small intestine is the duodenum into which the ducts of liver and pancreas open. The portion next to the duodenum is the ileum. Absorption of digested food takes place through the ileum.
Small intestine has many finger like processes called villi which increase the area for absorption. The remaining undigested food enters into the large intestine .If any water left behind is absorbed by the wall of the large intestine.
The solid wastes are excreted out through the cloaca. The intestine is kept intact by a membrane which prevents the strangulation of the small intestine and the membrane is called mesentery.