peristalsis
Meaning of peristalsis: The gut runs a nervous system of its own, so the waves carry on even when signals from the brain are absent.
Definition of peristalsis
Peristalsis is the wave of muscle contraction that moves contents along a hollow tube in the body. A ring of muscle tightens behind the material while the muscle just ahead relaxes, and that pattern travels forward, pushing the contents along. It works against gravity, which is why swallowing succeeds perfectly well while lying down.
Where does it happen?
| Tube | What is moved | Character |
|---|---|---|
| Esophagus | A swallowed mouthful | A single strong wave, seconds long |
| Stomach | Food being ground and mixed | Rhythmic waves toward the outlet |
| Small intestine | Partly digested material | Short pushes, mixed with side to side churning |
| Colon | Stool | Slow, with occasional long sweeping movements |
| Ureter | Urine from kidney to bladder | Regular squeezes, independent of the gut |
Swallowing begins under voluntary control, because the top of the esophagus is made of the same striated muscle as a limb. Below that the wall is smooth muscle, and control passes out of conscious reach entirely.
What controls the wave?
The digestive system carries its own network of nerve cells embedded in the gut wall, numerous enough that it is sometimes described as a second brain. It can generate and coordinate peristalsis with no input from the brain or spinal cord, which is why an isolated segment of intestine still produces waves. Specialized pacemaker cells within the wall set an underlying electrical rhythm, and stretching the wall from within triggers the reflex: nerves release messengers that contract the muscle behind the material and relax it ahead. The brain modulates the pace through the vagus nerve and through stress responses, but it does not command each wave.
What happens when it fails?
Slowing produces bloating, nausea, constipation and a feeling of fullness. Handling of the abdomen during surgery commonly stops bowel movement for a period afterward, and opioid medication slows transit markedly by acting on receptors in the gut wall itself. Nerve damage from long standing diabetes can leave the stomach emptying sluggishly. Some disorders are structural in the nerve supply: a segment born without the nerve cells cannot relax and blocks passage, and loss of coordination in the esophagus prevents the lower valve from opening on cue. Listening for bowel sounds is the simplest bedside check that the waves have resumed.
Used in a sentence
Bowel sounds were assessed to evaluate the patient's peristalsis following abdominal surgery.
Good to know
Peristalsis can be slowed by opioid medication and by conditions affecting the nerves of the gut wall, a frequent contributor to constipation that has nothing to do with diet.
Word origin
Where “peristalsis” comes from
Formed from peri-, Greek for around, and stalsis, from stellein, meaning to constrict or place.