Gastroenterology: Understanding the Digestive System
The mouth is the beginning of the GI tract, where food is ingested and chewing breaks food into smaller pieces with saliva beginning the breakdown process. Saliva contains an enzyme called salivary amylase that starts the digestion of carbohydrates. The esophagus is a muscular tube that transports the food from the mouth to the stomach through peristaltic contractions.
Gastroenterology in the stomach, protein-digesting enzymes and hydrochloric acid are released to continue the breakdown of food. The contents of the stomach, now called chyme, exit through the pyloric sphincter into the small intestine over several hours. The small intestine, made up of the duodenum, jejunum and ileum, is where the majority of digestion and nutrient absorption takes place. Pancreatic juices containing digestive enzymes like trypsin and lipase as well as bile from the liver and gallbladder further break down proteins, fats, and carbohydrates into absorbable molecules like amino acids, fatty acids, glycerol, and sugars. The intestinal walls contain villi and microvilli that act to increase absorption surface area.
Once nutrients have been extracted, the remnants move into the large intestine where water is absorbed and the waste matter is compacted into stool. The appendix and cecum connect the small and large intestines. The colon makes up the main portion of the large intestine and is where most water is absorbed before the semi-solid waste moves into the rectum for storage until defecation through the anal canal. The gastrointestinal system works in harmony with other regulatory systems to keep the digestive process running smoothly.
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