| Volume and pH of intestinal secretions
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| Maintaining the appropriate pH in different parts of the GI tract is crucial for the digestive process, and also for the preservation of the underlying tissues. Thus, saliva secreted in the mouth, due to its bicarbonate content, is alkaline. The lumen of the stomach is strongly acidic, while the mucus lining its walls is again alkaline. The acidic content of the stomach is then neutralized by the strongly alkaline pancreatic juice.
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| Intestinal secretions reach the volume of about 7.5 liters a day. This is in addition to the average water intake of about 1.5L. In normal circumstances only about 150-250 mL of water is contained in the stool, the rest being absorbed in the GI tract.
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| page 114 |  | | page 115 |
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Table 9-1.
Organization of the GI tract in relation to functional requirements. |
| Body_ID: None |
| Gastrointestinal (GI) tract organization by functional requirements |
| Body_ID: T009001.50 |
| Gastrointestinal organ | Primary function in absorption of foodstuffs |
| Body_ID: T009001.100 |
| salivary glands | production of fluid and digestive enzymes for homogenization, lubrication and digestion of carbohydrate (amylase) and lipid (lingual lipases) |
| Body_ID: T009001.150 |
| stomach | secretion of HCl and proteases to initiate hydrolysis of proteins |
| Body_ID: T009001.200 |
| pancreas | secretion of HCO- 3, proteases and lipases to continue digestion of proteins/lipids and amylase to continue digesting starch |
| Body_ID: T009001.250 |
| liver/gall bladder | secretion and storage of bile acids for release to small bowel |
| Body_ID: T009001.300 |
| small bowel | final intraluminal digestion of foodstuffs, digestion of carbohydrate dimers, and specific absorptive pathways for digested material |
| Body_ID: T009001.350 |
| large bowel | absorption of fluid and electrolytes and products of bacterial action in the colon |
| Body_ID: T009001.400 |
| Loss of fluid from the gastrointestinal tract may leads to disturbances of fluid, electrolyte, and acid base balance
|
| Vomiting, i.e. the loss of primarily stomach contents, and diarrhoea, which causes the loss of intestinal contents, may lead to problems with water, electrolyte, and acid-base balance.
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| Prolonged vomiting causes the loss of water, potassium, and hydrogen ion. Diarrhoea might be caused by the increased intestinal secretion due to, for instance, inflammation, or may be caused by the malabsorption of nutrients. Severe diarrhoea may lead to dehydration and metabolic acidosis due to the loss of alkaline fluids. It also induces loss of sodium, potassium, and other minerals (see Chapters 10 and 22 for more details).
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