<P> Chyme results from the mechanical and chemical breakdown of a bolus and consists of partially digested food, water, hydrochloric acid, and various digestive enzymes . Chyme slowly passes through the pyloric sphincter and into the duodenum, where the extraction of nutrients begins . Depending on the quantity and contents of the meal, the stomach will digest the food into chyme in anywhere between 40 minutes to a few hours . </P> <P> With a pH of approximately 2, chyme emerging from the stomach is very acidic . The duodenum secretes a hormone, cholecystokinin (CCK), which causes the gall bladder to contract, releasing alkaline bile into the duodenum . CCK also causes the release of digestive enzymes from the pancreas . The duodenum is a short section of the small intestine located between the stomach and the rest of the small intestine . The duodenum also produces the hormone secretin to stimulate the pancreatic secretion of large amounts of sodium bicarbonate, which then raises pH of the chyme to 7 . The chyme then enters the jejunum, where the useful portion of it is transformed into chyle . (As the material moves through the jejunum and ileum, digestion progresses, and the nonuseful portion will continue onward into the large intestine .) The duodenum is protected by a thick layer of mucus and the neutralizing actions of the sodium bicarbonate and bile . </P> <P> At a pH of 7, the enzymes that were present from the stomach are no longer active . This then leads into the further breakdown of the nutrients still present by anaerobic bacteria, which at the same time help to package the remains . These bacteria also help synthesize vitamin B and vitamin K, which will be absorbed along with other nutrients . </P> <P> Chyme has a low pH that is countered by the production of bile, helping to further digest food . Chyme is part liquid and part solid: a thick semifluid mass of partially digested food and digestive secretions that is formed in the stomach and small intestine during digestion . Chyme also contains cells from the mouth and esophagus that slough off from the mechanical action of chewing and swallowing . </P>

The ph is not the same in all parts of the digestive system