Cambridge O Level Biology · Syllabus 5090 · Human Nutrition
Peristalsis
What is Peristalsis?
Waves of contraction and relaxation of the circular and longitudinal muscles in the wall of the alimentary canal, which move food along it. Circular muscle contracts behind the bolus, narrowing the canal and pushing the bolus forward, while circular muscle ahead relaxes so that the canal widens to receive it.
This definition is part of the Human Nutrition chapter in Cambridge O Level Biology.
Common mistakes with Peristalsis
- “Food moves down the gut because of gravity.” Why it is wrong You can swallow lying flat. Movement is produced by muscle, not by falling. Write instead "Peristalsis moves food along: circular muscle contracts behind the bolus and relaxes in front of it, and the wave travels along the canal."
Questions students ask about Peristalsis
Does food fall down the oesophagus?
No. Food is moved by peristalsis: waves of contraction and relaxation of the circular and longitudinal muscles in the wall of the canal. Circular muscle contracts behind the bolus and relaxes ahead of it, so the bolus is squeezed forward. This works in any body position, which is why you can swallow lying down.