Gastrointestinal tract (GI)

The gastrointestinal tract is the continuous tube from mouth to anus that digests food, absorbs nutrients and water, and hosts much of the body's immune and nervous tissue.

Its sections are the esophagus, stomach, small intestine and large intestine, supported by the liver, pancreas and gallbladder. Digestion breaks food into absorbable units, the small intestine absorbs most nutrients, and the colon recovers water and houses trillions of bacteria. The gut has its own network of nerves, the enteric nervous system, that coordinates movement and secretion and communicates with the brain, and its lining contains a large share of the body's immune cells.

Swallowed substances are absorbed across the intestinal wall and pass through the liver before reaching the general circulation, which lowers the amount of many compounds, including cannabinoids, that survives to act on the body. Common disorders include reflux, ulcers, irritable bowel syndrome, inflammatory bowel disease, nausea and diarrhea; in pets, vomiting and diarrhea are among the most frequent reasons for veterinary visits. Cannabinoid receptors are present throughout the gut, and cannabinoids have been studied in models of intestinal inflammation, with human evidence still early.