In this article we will discuss about the digestive structure of toad.

The digestive system consists of alimen­tary canal and its associated digestive glands. The alimentary canal is a long tube which starts from the mouth and ends in the cloaca. The alimentary canal is made up of four layers. The outermost layer is thin and called serous coat. Next to the serous coat lies the muscular layer which is composed of outer longitudinal muscles and the inner circular muscles.

The innermost layer lining the lumen is the mucous coat. The mucous layer is composed of epithelial cells and glands at certain regions. The region between the muscular coat and the mucous coat is filled up with connective tissue matrix with blood and lymphatic vessels. This layer is known as sub mucous coat.

The mouth is a wide aperture and is bounded by upper and lower jaws. Both the jaws are toothless. The mouth leads into a spacious buccal cavity. The roof of the buccal cavity contains a pair of internal nostrils, impressions of the eyeballs, a pair of eustachian apertures.

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The floor of the buccal cavity bears a large fleshy tongue which is attached to the hyoid arch. The tongue is fixed anteriorly but free behind. The tongue is kept sticky by the secretion of inter-maxil­lary glands. It can quickly be protruded to capture insects. Behind the tongue there is a longitudinal slit called glottis which leads into the laryngotracheal chamber.

There are mucous glands in the buccal cavity which do not produce any enzyme. There is a system of cilia in the buccal cavity which possibly keep the oral fluid in circulation. The buccal cavity narrows towards the pharynx which leads into a wide tube known as oesophagus or gullet.

The oesophagus opens into the stomach. The stomach is a thick-walled spa­cious sac and is slightly curved (Fig. 1.68A). The broad anterior part of the stomach is known as cardiac end and the other end is called pyloric end. The pyloric part of the stomach opens into intestine. This opening is guarded by circular sphincter muscle called pyloric valve which regulates the exit of food from the stomach.

The mucous coat of the stomach opens into intestine. This opening is guarded by circular spinster muscle called pyloric valve which regulates the exit of food from the stomach. The mucous coat of the stomach contains tubular gastric glands which secrete digestive juices and unicellular parietal glands (or oxyntic cells) which secrete hydrochloric acid.