The following statement is similar to the statements you will see on exams. Writ
ID: 67231 • Letter: T
Question
The following statement is similar to the statements you will see on exams. Write a short paragraph describing 1) whether the statement is correct or incorrect and 2) the reasoning behind your answers. Correct responses that demonstrate complete and thorough reasoning will receive full points.
When enterogastrone secretion is impaired, patients may experience decreased duodenal pH and duodenal ulcers. Write a paragraph describing a possible mechanism for this. Be sure to include a description of the normal stimuli for, targets of, and responses to enterogastrone in your answer. Your answer should also demonstrate your knowledge of the normal physiology of the duodenum.
Explanation / Answer
The best known digestive hormones are those of the stomach and duodenum. There may be others produced in other parts of the intestine as well, but evidence is lacking. Gastrin, the hormone produced in the stomach, favors the production of gastric acid secretions. The hormone is produced in response to vagal stimulation, which also produces gastric acid and pepsin secretion. However, it is produced even after the vagus is cut, meaning that local factors must also be involved.
The most important of these is apparently protein in the stomach. The breakdown of protein, initiated by the process set in motion by astrin or the vagus results in polypeptide formation; these further stimulate the secretion of gastrin; and fairly soon, the gastric secretion is maximal. The continued breakdown of foods through mechanical activity of the stomach assisted by the gastric secretions reduces the stomach contents to a point where they can be forced through the pylorus into the duodenum.
Until this time, it might seem that gastrin, rather than quenching the initiating stimulus, enhanced it. When, however, it is recalled that the taking of food results in the emptying of the stomach, it is quite clear that the stimulus, taking food into the stomach, is neutralized by the response, emptying the stomach.
It may be noted that alcohol also causes gastrin release. The widespread use of pre-dinner drinks has been interpreted to indicate that the digestive virtues of alcohol are somehow known to most people. Unfortunately for this argument, breakfast and lunch are digested by the same people who require alcoholic drinks before dinner without any discernable difficulties. It may be suspected that alcohol before dinner serves other digestive purposes.
The acid-food-pepsin mixture entering the duodenum provokes the release of five hormones: secretin, enterogastrone, cholecystokinin, pancreozymin, and villikinin.
Secretin brings about pancreatic secretion. The fluid produced is alkaline (neutralizing gastric juice) but quite poor in enzymes. Enzyme production is brought about by pancreozymin. Enterogastrone is produced in the same area. Acid and fat in the duodenum elicit the production of this hormone. Its effects are to reduce the motility and acid secretion of the stomach, an unlooked for effect, but a very useful one. Fat is digested rather slowly; enterogastrone appears to signal the stomach to empty slowly when fat is present, which leaves time for digestion of the fat already emptied.
The release of enterogastrone is associated with a longer emptying time for the stomach after a meal high in fat than one which is low in fat. When it is desirable to keep the stomach full for a long time, high fat diets are usually suggested, for they may act through enterogastrone production.
Functions of enterogastrone:
nterogastrone, a hormone secreted by the duodenal mucosa when fatty food is in the stomach or small intestine; it is also thought to be released when sugars and proteins are in the intestine. Enterogastrone is transported by the bloodstream to the glands and muscles of the stomach, where it inhibits gastric movements and secretions, possibly by blocking the production or activity of gastrin, the hormone that initially causes these functions. Enterogastrone may slow down stomach emptying by reducing the amount of acid produced. High acid content causes the valve between the stomach and intestine to relax, allowing food passage.
The chemical identity of enterogastrone is still uncertain. Substances from the intestine that were thought to be enterogastrone have been shown to be composed of not one but possibly as many as three independent hormones. Two of these hormones are now known as secretin and cholecystokinin. Consequently, many functions originally thought to be performed by enterogastrone have been reassigned to these other hormones.