The gastrocolic reflex is a stimulus response of the colon that occurs when the stomach is irritated. The gastrocolic reflex causes the colon to contract and the contents of the colon to be advanced toward the rectum.
What is the gastrocolic reflex?
The gastrocolic reflex is a stimulus response of the colon that occurs when the stomach is irritated. In the gastrocolic reflex, the colon responds to irritation of the stomach and upper digestive organs. The term reflex is actually not quite correct, as it is more of a stimulus response from the colon. An actual reflex occurs much more quickly. As a rule, the gastrocolic reflex is triggered by food intake and causes so-called mass movements in the colon. These move the intestinal contents toward the rectum and ultimately cause bowel emptying.
Function and task
To understand the gastrocolic reflex, knowledge of the digestive process is necessary. The first digestion of food already occurs in the mouth. Here, the food is crushed by the teeth and made slippery by salivation. The food pulp then passes through the esophagus into the stomach. There it is collected for a longer period of time. The gastric mucosa contains different types of cells, all of which play an important role in digestion. The accessory cells produce mucus to protect the mucosa, the accessory cells produce hydrochloric acid and the so-called intrinsic factor, and the primary cells produce pepsinogens. These are important for protein digestion. So the actual digestion begins in the stomach. In addition, the food pulp is mixed there and pushed through the stomach outlet into the small intestine. In the small intestine, especially in the duodenum, carbohydrate, protein and fat digestion takes place. In addition, water is removed from the food pulp here. Up to 80% of water, consisting of digestive juices and liquid from the ingested food, is absorbed here. The food pulp then passes from the small intestine into the large intestine. The large intestine has a typical structure for the gastrointestinal tract. The innermost layer, a mucosal layer, is covered by loose connective tissue. This is followed by a ring muscle layer and a longitudinal muscle layer. A nerve plexus lies between the muscle layers. This is also known as the myenteric plexus. The myenteric plexus is responsible for the muscular activity of the digestive organs, especially the muscular activity of the intestines. The longitudinal muscle layer of the intestine is thickened into three strands called teenae. The annular muscle layer has retractions. There, the intestinal wall forms bulges. These bulges are called haustra. The taenia and haustrena, which are characteristic of the colon, support the peristalsis of the intestine. In the colon, a distinction is made between non-propulsive and propulsive peristalsis. Non-propulsive peristalsis consists of annular contractions. It serves to mix the food pulp in the intestine. Propulsive peristalsis is characterized by involvement of the longitudinal muscles. It serves to transport the contents of the intestine further in the direction of the anus. There are stretch receptors in the wall of the mouth, esophagus and stomach. When food is ingested, the wall of these organs is stretched, thereby exciting the receptors. This information is now transmitted to the large intestine via the autonomic nervous system on the one hand and via the myenteric plexus on the other. The colon reacts with strong contractions and increased propulsive peristalsis. As a result, the food pulp in the large intestine is pushed further and further towards the rectum. There, the stretching of the rectal wall then triggers the urge to defecate and, ideally, this is followed by defecation. So, simply put, the gastrocolic reflex ensures that space is made in the colon for digestion of the newly ingested food.
Diseases and ailments
Consequently, digestive disorders occur when the gastrocolic reflex is impaired. A congenital disorder of the gastrocolic reflex is found in Jirásek-Zuelzer-Wilson syndrome. Affected individuals lack the nerve cells of the myenteric plexus in the colon wall. This results in an enlargement of the intestine. This is also known as megacolon. In addition, the stool cannot pass through the colon properly. Sufferers of the disease already suffer from a distended abdomen in infancy and have problems with defecation. A characteristic feature is delayed settling of the meconium after birth.Meconium, popularly known as puerperal sputum, is the infant’s first bowel movement. Diagnosis is made by X-ray and histological examination of the colon tissue. Often, newborns must have an artificial anus placed just a few days after birth. The passage of stool may have to be surgically restored. A similar disease of the intestine with disturbed gastrocolic reflex is Hirschsprung’s disease. Here, too, nerve cells in the area of the myenteric plexus are missing. In addition, nerve cells responsible for stimulating the ring muscles are increased. This results in permanent excitation of the ring musculature with simultaneous nervous undersupply of the longitudinal musculature. The ring musculature contracts and constricts the intestine. Intestinal obstruction results. Due to the lack of gastrocolic reflex, the intestinal contents are not transported further. The intestine can no longer be emptied. The result is severe constipation. Due to the fecal stasis, the intestine dilates and megacolon occurs in this case as well. As in Jirásek-Zuelzer-Wilson syndrome, the child’s urine does not pass or is very delayed. An increased gastrocolic reflex may also cause problems. In particular, neonates and patients with irritable bowel syndrome are affected by an increased gastrocolic reflex. Normally, the gastrocolic reflex causes defecation within 30 to 60 minutes after food intake. With an increased gastrocolic reflex, those affected often have to go to the toilet while eating. The premature urge to defecate is accompanied by violent abdominal cramps. Diarrhea often occurs. Newborns with an increased gastrocolic reflex often refuse food completely because of the extremely painful intestinal cramps.
