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Gastrointestinal physiology is the branch of human physiology that addresses the physical function of the gastrointestinal (GI) tract.The function of the GI tract is to process ingested food by mechanical and chemical means, extract nutrients and excrete waste products.
The stomach is a distensible organ and can normally expand to hold about one litre of food. [22] This expansion is enabled by a series of gastric folds in the inner walls of the stomach. The stomach of a newborn baby will only be able to expand to retain about 30 ml.
The gastric folds (or gastric rugae) are coiled sections of tissue that exist in the mucosal and submucosal layers of the stomach. [1] They provide elasticity by allowing the stomach to expand when a bolus enters it. These folds stretch outward through the action of mechanoreceptors, which respond to the increase in pressure. [2]
The human gastrointestinal tract consists of the esophagus, stomach, and intestines, and is divided into the upper and lower gastrointestinal tracts. [3] The GI tract includes all structures between the mouth and the anus , [ 4 ] forming a continuous passageway that includes the main organs of digestion, namely, the stomach , small intestine ...
Occasionally in the large intestine (2-3 times a day), there will be mass contraction of certain segments, moving a lot of faeces along. This is generally when one gets the urge to defecate. The pylorus of the stomach has a thickened portion of the inner circular layer: the pyloric sphincter. Alone among the GI tract, the stomach has a third ...
Pepsin is a protease that can digest and damage stomach cells. To prevent these disastrous effects, mucus and bicarbonate ions (HCO 3 −) are secreted by the foveolar cells. The mucus allows the acid at pH above 4 to penetrate lining, but below pH 4 (i.e. when acid is more concentrated) the acid cannot penetrate the mucus.
The stomach is distensible, and can normally expand to hold about one litre of food. [3] In a newborn human baby the stomach will only be able to hold about 30 millilitres. The maximum stomach volume in adults is between 2 and 4 litres, [4] [5] although volumes of up to 15 litres have been observed in extreme circumstances. [6]
When the stomach pH decreases (becomes more acidic), the ECLs stop releasing histamine. G cells – They secrete gastrin hormone. Gastrin stimulates the gastric glands to release gastric acid. These cells are mostly found in pyloric glands in the pyloric antrum; some are found in the duodenum and other tissues. The gastric pits of these glands ...