Peristalsis: The Digestive Muscle Movement

Peristalsis is the series of muscle contractions that propel food through the digestive tract, from the pharynx (throat) to the anus. This movement is controlled by the enteric nervous system (ENS) and is an involuntary process.

How Peristalsis Works

The process begins with the formation of a bolus, a mixture of chewed food and saliva, which passes down the throat. The muscles of the digestive tract, including the esophagus, stomach, small intestine, and large intestine, contract in a sequential and rhythmic manner. This movement is coordinated by two types of muscles: longitudinal and circular muscles.

The Role of Hormones and Muscles

The brain releases the hormone serotonin, which stimulates the contractions that result in peristalsis. The longitudinal muscles contract to narrow the esophagus, propelling food downwards. The circular muscles then expand, allowing the food to pass through. This alternating movement creates the peristaltic wave.

Peristalsis in the Digestive Tract

As food passes through each stage of the digestive tract, it undergoes changes in mixing and absorption:

– Esophagus: Food passes through the gastroesophageal sphincter into the stomach.
– Stomach: Food is mixed with acidic stomach juice and churned by stomach muscles.
– Small intestine: Nutrients are absorbed through slower peristaltic movements.
– Large intestine: Waste is propelled forward with slower contractions.

Problems with Peristalsis

Disorders that affect peristalsis include:

– Gastro-esophageal reflux disease (GERD)
– Gastroparesis (lack of communication between muscles)
– Hirschsprung disease (defect in enteric nervous system)
– Achalasia (flap that allows contents to pass from esophagus to stomach does not open)

Peristalsis in Other Organ Systems

Peristalsis also occurs in other organ systems, including:

– Lymphatic system: Lymphatic fluid is propelled forward through peristalsis.
– Reproductive system: Sperm is propelled through the vas deferens by reflexive contractions of smooth muscles.

References

https://en.wikipedia.org/wiki/Peristalsis
https://www.ncbi.nlm.nih.gov/books/NBK556137/
https://www.sciencedirect.com/topics/medicine-and-dentistry/peristalsis
https://www.visiblebody.com/learn/digestive/digestive-propulsion-and-peristalsis