Digestive System of Snakes
Since reptiles were the first to inhabit dry land, several evolutionary changes were required in the anatomy of reptiles. One aspect of these evolutionary changes includes the digestive system.
Many of these adaptations can be seen in the mouth of snakes. Since snakes are terrestrial, many changes occur in the oral glands in the transition from amphibian to reptiles. These changes in oral glands and venom glands aid in the immobilizing prey and swallowing prey. The salivary glands found in snakes include the palatine, lingual, sublingual and labial gland. These glands help moisten the prey for swallowing. In venomous snakes, such as the Water Moccasin, poison glands are modifications of the labial glands. These glands lie on either side of the head and neck and lead to ducts in the modified maxillary teeth. The teeth of snakes also underwent evolutionary changes. Members of Squamata have pleurodont dentition. Venomous snakes have grooved or tubular teeth for the injection of venom. Vipers have large retractable, tubular teeth (solenoglyphous).
Directly inside the mouth of snakes is the buccal cavity. This leads to the esophagus of the snake. In snakes, the esophagus is long and can cover up to half the length of the body. The esophagus of snakes has more internal folds than other reptiles, which allows for the swallowing of large, whole prey. Peristaltic movement within the esophagus moves the food downward towards the stomach.
The stomach is a j-shaped organ in which most of the digestion occurs in snakes. The cells of the stomach secrete digestive enzymes and gastric juices that breakdown proteins. The food then passes through the pyloric valve and into the small intestines.
The small intestines is a long narrow coiled tube where absorbance of nutrients takes place. The small intestines is divided into three regions: the duodenum, the ileum, and jejunum. The liver, which primarily functions in excreting nitrogenous wastes, storing nutrients, and producing bile, excretes digestive enzymes into the duodenum of the small intestines. Also, the pancreas, which produces insulin and glycogen as well, produces digestive enzymes such as lipases, proteases and carbohydrases and secretes them into the duodenum.
At the junction of the small intestines and large intestines is the caecum. The large intestines is the least muscular and most thin-walled structure of the snake digestive system. It passes into the cloacae chamber. This chamber is divided into a copradaeum for receiving feces and a urodaeum for urine and products of the genital organs. The cloaca plays an important role in the reabsorption of water.
The rate of digestion is dependent of body temperature because they are cold-blooded animals.
Goin, Coleman J. Intro to Herpetology. San Francisco: W.H. Freeman and Company, 1962.
Spellerberg, Ian. Biology of Reptiles. NY: Chapman and Hall, 1982.