Edexcel iGCSE Biology-2.28 how food is moved through the gut- Study Notes- New Syllabus

Peristalsis – Movement of Food Through the Gut

📝 Introduction

Once food is swallowed, it doesn’t just “fall” down by gravity.
Instead, it is pushed along the gut by a process called peristalsis.

🔑 What is Peristalsis?

• Definition: Peristalsis is the wave-like contraction and relaxation of muscles in the walls of the alimentary canal that pushes food forward.
• Occurs from oesophagus → rectum (whole gut length).
• Fun fact: Works even if you’re upside down!

🧩 How it Works

• The gut wall has two muscle layers:
  • Circular muscles → run around the tube.
  • Longitudinal muscles → run lengthwise along the tube.
• Coordinated movement produces the peristaltic wave:
  • Behind the bolus → circular muscles contract → squeezes food forward.
  • In front of the bolus → circular muscles relax + longitudinal contract → widens tube.
  • Food is pushed along like toothpaste from a tube.

📍 Importance of Peristalsis

• Keeps food moving in one direction.
• Mixes food with digestive juices → ensures proper digestion.
• Helps absorption by moving food over villi in small intestine.
• Works independently of gravity → swallowing works lying down.

📊 Summary Table

⚡ Quick Recap
Peristalsis = wave-like muscle movements.
Circular contracts behind, longitudinal contracts in front.
Pushes food → mixes with enzymes → aids absorption.
Not dependent on gravity.