Intestinal Peristalsis: Function, Tasks, Role & Diseases

Peristalsis refers to the muscular activity and resulting movements of hollow organs. Intestinal peristalsis serves primarily to mix the food pellet and convey it toward the rectum or anus. In some cases, the term intestinal peristalsis is used synonymously with terms such as intestinal movements or intestinal motility. However, intestinal peristalsis actually includes propulsive and non-propulsive peristalsis alone. All other intestinal movements tend to fall under the term intestinal motility.

What is intestinal peristalsis?

The primary purpose of intestinal peristalsis is to mix the food pulp and move it toward the rectum or anus. A pattern of movement of hollow organs that results from synchronous activity of smooth muscle cells is called peristalsis. Typical peristalsis is wave-like with alternating phases of contraction and relaxation of the musculature. Intestinal peristalsis is based on contraction and relaxation of the longitudinal and annular muscles of the intestine. It is found throughout the intestine, that is, both in the sections of the small intestine and in the large intestine. The intestine has a special wall structure for this function. The innermost layer of the intestinal wall is the tunica mucosa, a layer of mucous membrane. On top of this lies a muscular layer consisting of a ring muscle layer (stratum circulare or stratum anulare) and a longitudinal muscle layer (stratum longitudinale). The outermost intestinal layer is called tunica adventitia. Only through the longitudinal and the annular muscles is the special intestinal peristalsis possible at all.

Function and task

In the intestine, a distinction can be made between propulsive and nonpropulsive intestinal peristalsis. Nonpropulsive peristalsis arises from annular, locally occurring waves of contraction and is also known as segmentation. Its main purpose is to mix the food pulp (chyme) in the intestine. In propulsive peristalsis, the annular musculature also contracts, but the movement is continued with the involvement of the longitudinal musculature. This is also referred to as tonic continuous contraction of the intestinal musculature. Propulsive peristalsis serves to transport the chyme further in the direction of the anus. In addition to these two forms of intestinal peristalsis, a differentiation can be made between retrograde and orthograde peristalsis. In orthograde peristalsis, the intestinal contents are transported in the correct direction, i.e., toward the rectum. In retrograde peristalsis, the direction of transport is reversed. In order to slow down the transit time of the food pulp through the intestine, this condition can be created surgically in humans. The control of intestinal peristalsis is subject to the so-called pacemaker cells. They determine the rhythm of peristalsis. The pacemaker cells in the smooth muscle of the gastrointestinal tract are also called interstitial Cajal cells (ICC). They are spindle-shaped cells located in the longitudinal muscle layer of the intestine. They act as a kind of mediator between the muscle cells and the excitatory as well as inhibitory neurons of the intestine. There exists another group of Cajal cells in the intestinal muscles. These form a branched connection between the longitudinal and the ring muscles and are the actual pacemakers. They are closely connected to the so-called Auerbach’s plexus. The Auerbach’s plexus is a nerve plexus in the intestinal wall and is responsible for intestinal peristalsis and in particular for controlling the contractions of the smooth muscle cells. The pacemaker cells, in turn, are subject to the control of the autonomic nervous system. Although the musculature also has some rhythmicity of its own, increased peristalsis may be required depending on food intake. The peristaltic reflex is responsible for increased intestinal peristalsis after food intake. Within the stomach wall and intestinal wall are mechanoreceptors that respond to distension. When the stomach or intestines are stretched by the ingested food, the cells of the enteric nervous system release serotonin. This stimulates other nerve cells in the intestinal wall, including the pacemaker cells. These, in turn, cause the intestinal muscle cells to contract.

Diseases and disorders

Disturbances in intestinal peristalsis can occur in various diseases.In paralytic ileus, a form of intestinal obstruction, peristalsis comes to a complete standstill due to a functional disorder, resulting in intestinal paralysis. The intestinal passage is interrupted and there is a stagnation of food pulp and feces in the intestine. The most common trigger of paralytic ileus is an inflammation in the abdominal cavity, such as appendicitis, gallbladder inflammation or pancreatitis. Vascular occlusion, pregnancy, or various medications such as opiates, antidepressants, and medications for Parkinson’s disease can also result in paralytic ileus. Whereas in paralytic ileus intestinal peristalsis stops completely, in mechanical ileus it is even partially increased. In mechanical ileus, intestinal transit is prevented by a mechanical obstruction inside the intestine. Mechanical ileus may be due to fecal balls, foreign bodies, gallstones, intestinal obstruction, or intestinal obstruction. Mechanical ileus can also occur as a complication of an umbilical or inguinal hernia. In a mechanical ileus, the intestine makes an increased attempt to move the food pulp past the obstruction. Therefore, peristalsis is increased in the section of intestine in front of the obstruction. Typical symptoms of an intestinal obstruction include vomiting, possibly even vomiting of feces, bloating within the intestine, and complete stool and wind retention. Ileus can cause severe damage to the intestinal wall, allowing bacteria to spread from the intestine into the abdomen, where they can cause life-threatening inflammation of the peritoneum. In irritable bowel syndrome, intestinal peristalsis is almost always disturbed as well. Irritable bowel syndrome is the most common disease of the intestine. It is a chronic functional disorder with an unknown cause. The symptoms of irritable bowel syndrome are very diverse. The disturbed peristalsis results in diarrhea alternating with constipation, stomach pain, bloating and flatulence. Emptying the stool is often painful. The patient’s condition worsens, especially in stressful situations. Some physicians therefore include irritable bowel syndrome among the psychosomatic diseases.