- Key People:
- Ernest Henry Starling
- Sir William Maddock Bayliss
- Related Topics:
- digestion
- gastrocolic reflex
peristalsis
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What is peristalsis?
Peristalsis is a series of involuntary wave-like muscle contractions that occur in hollow tubes of the body, most notably in the digestive tract. These contractions move food and waste materials through the digestive system. In the esophagus, peristaltic waves push food down to the stomach, and secondary waves clear any remaining food particles. The stomach uses peristalsis to mix its contents and propel food into the small intestine. In the large intestine, mass movements push waste toward the anus, leading to defecation.
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Where does peristalsis occur in the human body?
Peristalsis occurs primarily in the digestive tract, involving involuntary movements of circular and longitudinal muscles in hollow tubes.
Peristaltic waves appear in the esophagus, pushing food to the stomach, and in the stomach, mixing contents and propelling food to the small intestine. In the small intestine, local stimulation causes contractions for absorption and movement. In the large intestine, continuous waves advance toward the anus, pushing waste, and reverse waves store unevacuated feces.
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How does peristalsis help with digestion?
Peristalsis involves involuntary muscle contractions that occur in the digestive tract and other hollow tubes in the body. These progressive, wavelike movements push food through the esophagus into the stomach.
In the stomach, peristaltic waves mix contents and propel food to the small intestine. In the small intestine, local stimulation from food particles causes contractions that expose food to the intestinal wall for absorption and move it forward. In the large intestine, peristaltic waves push waste toward the anus, leading to defecation. Reverse peristalsis in the colon can return feces for longer storage.
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What muscles are involved in peristalsis?
Peristalsis involves the coordinated action of involuntary longitudinal and circular muscles in the digestive tract and other hollow tubes of the body. These muscles contract in a progressive, wavelike motion.
The myenteric plexus, a network of neurons in the gastrointestinal tract, regulates these peristaltic waves, which propel digestive products from the mouth to the anus. The enteric nervous system controls gastrointestinal motility and secretion.
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How does peristalsis differ in the esophagus versus the intestines?
Peristalsis involves involuntary muscle contractions that propel contents through the digestive tract. In the esophagus, strong peristaltic waves begin at the top and push food down to the stomach in about nine seconds. Secondary waves clear any remaining food particles.
In the small intestine, local stimulation from food causes contractions that move in both directions, but those moving away from the mouth persist. These irregular waves mix food and expose it for absorption. In the large intestine, continuous mass movements push waste toward the anus, triggering defecation. Reverse peristalsis can return feces for longer storage. These waves also help remove gas and control bacteria.
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What can happen if peristalsis does not work properly?
If peristalsis does not work properly, a lack of coordination in the intestinal wall can cause excess contents to accumulate in the intestinal lumen, leading to distension, pain, and hyperactive contractions. Disturbed motility in the small intestine can result from unsuitable food additives or components. Intestinal obstruction may occur due to blockage by tumors or gallstones. A serious condition, ileus, or obstruction of the bowel, can also arise, potentially leading to necrosis and peritonitis. In the large intestine, impaired peristalsis can hinder the removal of gas and disrupt the balance of bacteria.
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peristalsis, involuntary movements of the longitudinal and circular muscles, primarily in the digestive tract but occasionally in other hollow tubes of the body, that occur in progressive wavelike contractions. Peristaltic waves occur in the esophagus, stomach, and intestines. The waves can be short, local reflexes or long, continuous contractions that travel the whole length of the organ, depending upon their location and what initiates their action.
In the esophagus, peristaltic waves begin at the upper portion of the tube and travel the whole length, pushing food ahead of the wave into the stomach. Particles of food left behind in the esophagus initiate secondary peristaltic waves that remove leftover substances. One wave travels the full length of the tube in about nine seconds. The peristaltic-wave contractions in the esophagus of humans are weak compared with those of most other mammals. In cud-chewing animals, such as cows, reverse peristalsis can occur so that the food is brought back from the stomach to the mouth for rechewing.
When the stomach is filled, peristaltic waves are diminished. The presence of fat in a meal can completely stop these movements for a short period until it is diluted with gastric juices or removed from the stomach. Peristaltic waves start as weak contractions at the beginning of the stomach and progressively become stronger as they near the distal stomach regions. The waves help to mix the stomach contents and propel food to the small intestine. Usually, two to three waves are present at one time in different regions of the stomach, and about three waves occur each minute.
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In the small intestine, local stimulation of the intestinal smooth muscle by the presence of food particles causes contractions that tend to travel from the stimulated point in both directions. Under normal circumstances, the progress of the contractions in an oral direction is quickly inhibited, while the contractions travelling away from the mouth tend to persist. If the intestine is paralyzed by applying such drugs as nicotine or cocaine to the intestinal wall, the contractions initiated by local stimulations travel equally well in both directions. Ordinarily, peristaltic waves appear in the small intestine at irregular intervals and travel for varying distances; some travel only a few inches, others a few feet. They serve to expose food to the intestinal wall for absorption and to move it forward.
In the large intestine (or colon), the peristaltic wave, or mass movement, is continuous and progressive; it advances steadily toward the anal end of the tract, pushing waste material in front of the wave. When these movements are vigorous enough to pass fecal masses into the rectum, they are followed by the desire to defecate. If feces are passed to the rectum and not evacuated from the body, they are returned to the last segment of the colon for longer storage by reverse peristaltic waves. Peristaltic waves are particularly important in helping to remove gas from the large intestine and in controlling bacterial growth by mechanically acting as a cleansing agent that dislodges and removes potential colonies of bacteria.