One idea is that people with IBS have a large intestine (colon) that is sensitive to certain foods and stress. The immune system may also be involved.
Stomach. After food enters your stomach, the stomach muscles mix the food and liquid with digestive juices.
Patients with these diseases also suffer from extraintestinal symptoms including joint pain and red eye, which can signal a flare of the disease. Esophagitis is inflammation of the esophagus and is a non-congenital condition.
Gallbladder surgery (cholecystectomy). People who have had their gallbladders removed have significantly more bile reflux than do people who haven’t had this surgery. Acid reflux occurs when the sphincter muscle at the lower end of your esophagus relaxes at the wrong time, allowing stomach acid to back up into your esophagus. This can cause heartburn and other signs and symptoms.
The Small Intestine/Bowel
TRPV1-positive nerve fibers occur in mucosa, musculature and enteric nerve plexuses of the rat, guinea-pig and mouse gut. Since enteric neurons usually do not stain for TRPV1, it follows that the TRPV1-positive nerve fibers in the GI tract represent processes of spinal afferents and, in the stomach, of some vagal afferents (13,33). Further analysis has revealed that the majority of nodose ganglion neurons projecting to the stomach and of DRG neurons projecting to the gut of rats express TRPV1 (13,33). It remains to be elucidated whether the TRPV1-like immunoreactivity which some investigators have seen in guinea-pig, porcine and human enteric neurons and rat gastric epithelial cells (13) is authentic TRPV1 or represents a nonfunctional protein such as TRPV1-Î² derived from alternative splicing of the trpv1 gene (40). The role of ASICs in acid sensing within the GI tract has not yet been extensively studied, with the exception of one study in the mouse stomach.
However, this has not been proven. Gastrin is a hormone produced by the stomach, which stimulates the release of gastric acid.
These projections increase the surface area of the small intestine, allowing the chyme to contact more of the small intestine wall. The increased contact causes more efficient food absorption. In the stomach, food undergoes chemical and mechanical digestion. Here, peristaltic contractions (mechanical digestion) churn the bolus, which mixes with strong digestive juices that the stomach lining cells secrete (chemical digestion). The stomach walls contain three layers of smooth muscle arranged in longitudinal, circular, and oblique (diagonal) rows.
Acid-sensing ion channels (ASICs)
When the stomach is full, the part of the brain that detects satiety signals fullness. There are three overlapping phases of gastric control-the cephalic phase, the gastric phase, and the intestinal phase-each requires many enzymes and is under neural control as well.
Thus, the stomach holds food and parses only small amounts into the small intestine at a time. Foods are not processed in the order they are eaten; rather, they are mixed together with digestive juices in the stomach until they are converted into chyme, which is released into the small intestine. Although a minimal amount of carbohydrate digestion occurs in the mouth, chemical digestion really gets underway in the stomach. An expansion of the alimentary canal that lies immediately inferior to the esophagus, the stomach links the esophagus to the first part of the small intestine (the duodenum) and is relatively fixed in place at its esophageal and duodenal ends. In between, however, it can be a highly active structure, contracting and continually changing position and size.
In fact, the surface epithelium of the stomach is completely replaced every 3 to 6 days. The intestinal phase of gastric secretion has both excitatory and inhibitory elements.
Large intestine. In your large intestine, more water moves from your GI tract into your bloodstream. Bacteria in your large intestine help break down remaining nutrients and make vitamin K.
Large intestine. Waste products from the digestive process include undigested parts of food, fluid, and older cells from the lining of your GI tract. The large intestine absorbs water and changes the waste from liquid into stool. Peristalsis helps move the stool into your rectum.
Bile and stomach acid can reflux into the esophagus when another muscular valve, the lower esophageal sphincter, malfunctions. The lower esophageal sphincter separates the esophagus and stomach. The valve normally opens just long enough to allow food to pass into the stomach. But if the valve weakens or relaxes abnormally, bile can wash back into the esophagus. Unlike gastric acid reflux, bile reflux can’t be completely controlled by changes in diet or lifestyle.
In summary, HCl in the stomach lumen accomplishes four things. It helps break down ingested tissues for attack by digestive enzymes; it provides the correct pH for the action of those enzymes; it converts a catalytically inactive proenzyme to an active enzyme (as we just saw); and it destroys invading microorganisms in the stomach contents.