Oesophagus 

The Oesophagus or the Food pipe is a muscular tube that transports chewed food from the mouth to the stomach through a process called peristalsis. 

Think of the esophagus as a water slide in a theme park. Just as the water slide carries you smoothly from the top to the bottom, the esophagus carries the food from the mouth to the stomach in a smooth, controlled manner.

Peristalsis

Peristalsis is defined as the wave-like coordinated, rhythmic muscular contraction and relaxation of the muscles primarily the esophagus, stomach, and intestines, that propels the contents through the digestive system. 

The process of peristalsis is involuntary (that means it’s not in conscious control). The muscle contractions involved in peristalsis are usually smooth muscle contractions, circular muscles and longitudinal muscles. These muscles are antagonistic muscles, which means if circular muscles contract, longitudinal muscles will relax and if longitudinal muscles contract, circular muscles will contract.

As shown in the diagram, the food is moving in the forward direction. This involves the circular muscles at point A to contract and longitudinal muscles to relax. At point B, longitudinal muscles contract while circular muscles are relaxed. 

Peristalsis is a series of coordinated muscular contractions that move ingested food and waste materials through the digestive system, allowing for digestion, nutrient absorption, and elimination of waste. It ensures that food and other materials move in one direction through the digestive tract, helping to facilitate the various processes of digestion and absorption.