Editing Digestion (section)

==Significance of pH==

Digestion is a complex process controlled by several factors. pH plays a crucial role in a normally functioning digestive tract. In the mouth, pharynx and esophagus, pH is typically about 6.8, very weakly acidic. Saliva controls pH in this region of the digestive tract. [[Salivary amylase]] is contained in saliva and starts the breakdown of carbohydrates into [[monosaccharides]]. Most digestive enzymes are sensitive to pH and will denature in a high or low pH environment.

The stomach's high acidity inhibits the breakdown of [[carbohydrates]] within it. This acidity confers two benefits: it [[Denaturation (biochemistry)|denatures]] proteins for further digestion in the small intestines, and provides [[Innate immune system|non-specific immunity]], damaging or eliminating various [[pathogens]].<ref>{{cite journal |last1=Beasley |first1=DeAnna E. |last2=Koltz |first2=Amanda M. |last3=Lambert |first3=Johanna E. |last4=Fierer |first4=Noah |last5=Dunn |first5=Rob R. |editor1-last=Li |editor1-first=Xiangzhen |title=The Evolution of Stomach Acidity and Its Relevance to the Human Microbiome |journal=PLOS ONE |date=July 2015 |volume=10 |issue=7 |pages=e0134116 |doi=10.1371/journal.pone.0134116 |pmid=26222383 |pmc=4519257 |bibcode=2015PLoSO..1034116B |doi-access=free }}</ref>

In the small intestines, the duodenum provides critical pH balancing to activate digestive enzymes. The liver secretes bile into the duodenum to neutralize the acidic conditions from the stomach, and the [[pancreatic duct]] empties into the duodenum, adding [[bicarbonate]] to neutralize the acidic chyme, thus creating a neutral environment. The mucosal tissue of the small intestines is alkaline with a pH of about 8.5.{{Citation needed|date=May 2011}}