The pylorus (stomach gate) represents the transition between the stomach outlet and the duodenum. It is responsible for ensuring that the contents of the stomach do not enter the small intestine until they are homogenized and do not return from there. The predominant complaints in this area occur as a narrowing in children.
What is the pylorus?
The pylorus (Greek: gatekeeper, guardian) is the part of the stomach located in the lower part. Synonymous names include gastric pylorus, gatekeeper, and sphincter (Latin: sphincter) pylori. As a ring-shaped sphincter, it closes the stomach outlet and ensures that the stomach contents are transported in portions to the intestine. It attaches to the distal part of the stomach as a thickened ring muscle of the stomach wall. The pylorus is located between the antrum pyloricum, the initial portion at the gastric outlet that lies immediately adjacent to the body of the stomach, and the duodenum. At rest, the pylorus is closed and is opened only under certain conditions.
Anatomy and structure
The pylorus includes the vestibule (antrum pyloricum), which is located at the exit of the stomach. This is followed by the pyloric canal (canalis pyloricus), which ends with the pylorus. The pyloric canal represents the transition from the stomach to the duodenum. The muscle that is active during opening and closing is called the sphincter pylori muscle. It closes around the opening at the bottom of the stomach (distal, away from the organ) that leads into the duodenum and is called the ostium pyloricum. This is open to the passage of fluid. It dilates as solid food particles arrive. Components of the autonomic nervous system (also: autonomic nervous system), which are involved in the control of processes that cannot be influenced voluntarily, are also part of the equipment of this part of the digestive tract, as well as special glands. These pyloric glands (Latin: glandulae pyloricae) have exocrine (exocrine, secreting outward) gland cells that produce a basic secretion that is not released into the blood. In addition, there are endocrine (endocrine, secreting inward) cells that secrete hormones into the surrounding blood. These hormones include gastrin, which is responsible for the production of acid in the stomach, and somatostatin, which is the antagonist, inhibiting the formation of gastric acid.
Function and tasks
Once the stomach has performed its tasks within digestion, the food pulp reaches the gastric outlet by peristaltic (Greek: peri, around; stellein, to set in motion) movements. They are triggered by a stimulus to the vagus nerve. This is localized in the brain, but is not involved in supply in the head region. It is the largest nerve in the parasympathetic system, which is part of the autonomic or vegetative nervous system and responsible for almost all organs and glands of the body. The rhythmic contractions of the musculature cause portion-by-portion emptying into the small intestine. Initially, a reflex (pyloric reflex) causes the opening to briefly open and allow a small portion (bolus) into the duodenum. Larger portions are passed on only after homogenization at the end of digestion in the stomach by more vigorous contractions. These contractions trigger a number of other processes. These, in turn, regulate further digestion as well as sensations such as hunger, feelings of fullness or satiety. The gatekeeper prevents the intestinal contents from flowing back. The alkaline secretions from the pyloric glands neutralize the acidic stomach contents. Gastrin, produced in the so-called G cells, releases gastric acid, which in turn acts on other processes within digestion. For example, it promotes motility (motility) of the small intestine and gallbladder and mediates the release of various substances.
Diseases
A disorder in the function of the pylorus affects the passage that leads into the small intestine. This may be impaired because of narrowing (pyloric stenosis). The pylorus does not open. Such changes are usually nervous and occur almost exclusively in children. Pylorospasm is a congenital disorder in infancy. Boys are affected more frequently than girls. The muscles are thickened and cramped. This leads to extreme tightness at the outlet and in this way to disturbances during gastric emptying. The infant vomits the stomach contents over and over again.Food intolerances or infections of the gastrointestinal tract must be differentiated diagnostically. Imaging techniques provide information about the presence of a disorder of the pylorus. Less common are space-occupying tumors that close the outlet. If the pylorus does not open regularly, gastric contents accumulate in the stomach and stimulate hydrochloric acid production. The concentration of gastric acid increases and there is a risk of attacking the stomach walls. An effect occurs when the contents of the duodenum flow back and reach the stomach (reflux). The cause of such phenomena is a non-closing pylorus. Diseases affecting hormone production are related to the formation of gastrin. Tumors that produce gastrin are called gastrinomas. Zollinger Ellison syndrome is a special form. The symptoms that occur are consequences of excessive gastrin production by tumors localized in the pancreas or duodenum. This massive increase in gastrin can be detected by a blood test. The hydrochloric acid producing cells are enlarged. About half of these are malignant.
Typical and common intestinal diseases
- Crohn’s disease (chronic inflammatory bowel disease)
- Inflammation of the intestine (enteritis)
- Intestinal polyps
- Intestinal colic
- Diverticula in the intestine (diverticulosis)
