2.28: Explain How and Why Food is Moved through the Gut by Peristalsis

PERISTALSIS: Wave-like muscle contractions that push food bolus down the Oesophagus from Mouth to Anus - occurs in Stomach and Gut

PERISTALSIS

Diagram showing the Process of Peristalsis

EXPLANATION: Peristalsis occurs as a result of the rhythmic contraction and relaxation of two muscles controlled unconsciously by the nervous system Circular muscle changes the radius of the Oesophagus, while the Longitudinal muscle changes length of Oesophagus Contraction of Circular muscle behind the food bolus constricts the gut to prevent bolus from being pushed back towards the Mouth Contraction of Longitudinal muscle where food bolus is located moves it along the gut As a result, wave-like muscle contractions occur which pushes the food bolus from Mouth to Anus

PURPOSE: As food bolus is pushed only a few centimetres at a time, progression through intestine is slow, allowing time for digestion This allows the churning of semi-digested food as they mix food bolus with enzymes, increasing rate of digestion