Digestion in snakes occurs in the esophagus, stomach, and small intestine portion of the gastrointestinal tract, while absorption occurs in the large intestine and cloaca. The swallowed prey is lubricated by the salivary secretions and mucous secretions and pushed through the esophagus into the stomach by waves of muscular contractions. The girth of the prey expands the stomach from it’s resting state (which is relaxed into rugae or folds) to accommodate the large food item and increase digestive surface area. Gastric glands coat the epithelium lining of the inner stomach wall secreting mucus, hydrochloric acid, and proteolytic enzymes. These enzymes and acids decrease the stomach PH from the range of 7 to 7.5 to the range of 1.5 to 4, depending on the snake’s body temperature and the prey item. This liquifies the prey into a slur called chyme, which enters the small intestine through the pyloric valve.
The intestines are lined with projections known as villi, which are lined with more projections known as microvilli. Together the projections increase the surface area of the intestines which increases the rate of digestion and absorption of the chyme. The pancreas produces digestive enzymes that are exported to the small intestine, while the liver secretes a product called bile that is carried from the gallbladder where it is stored to the small intestine via a system of ducts. The bile and digestive enzymes allow for further digestion, break down of fats, and neutralization of acid. Smooth muscles in the intestinal wall contract and relax in a wave-like motion that mixes the chyme and pushes it into the large intestine. Throughout the intestines, colonies of diverse gut bacteria are found forming a gut microbiome, they participate in the digestion of the food.
In the large intestines absorption of nutrients and water occurs through transportation across the intestinal wall into the blood circulation. The remaining undigested chyme forms feces, consisting mostly of gut bacteria, and keratinous proteins (hair, feathers, claws, beaks).
They empty into the cloaca where further water absorption forms a solid mass. Urinary products known as uric acid and urates empty from the kidneys into the cloaca, they are not water soluble so they are eliminated as a precipitate. Urates are commonly observed as a white/yellow solid excreted along with feces during defecation. A healthy and hydrated snake will have soft urates and feces, while a dehydrated snake will have hard waste which can become compacted.