Question

How long does food stay in the oesophagus?

Answer 1

Hint: Food is ingested inside the body through an opening called the mouth. The food has to reach the stomach where the breakdown of the food particles takes place. To do so, the food goes through the oesophagus by peristalsis movement.

Complete answer:
Swallowing or deglutition involves the passage of food bolus from the buccal cavity to the stomach. It is started as a voluntary action by pressing the tongue against the hard palate. This pushes the food bolus into the pharynx. From here, swallowing continues by involuntary action. The latter is started by stimulation of the sensory nerve endings in the pharynx. The swallowing reflex is controlled by the medulla of the brain. As the food reaches the pharynx, the soft palate and uvula rise to close the nasopharynx, and the larynx moves upward to meet the epiglottis for closing the glottis.

This stops breathing for movement and prevents the food from going the wrong way. Swallowing is normally so quick that we are unaware of the momentary interruption of breathing. Breathing during swallowing choke the respiratory passage. Entry of a piece of food into the glottis may pose a threat to life. Fortunately, the coughing reflex quickly clears the air passage.

The sphincter muscle at the beginning of the oesophagus relaxes for the purpose. The food bolus stretches the oesophagus and initiates another reflex action, causing the contraction of the circular muscle of the oesophagus wall above the bolus. As the food bolus is pushed down the oesophagus, it stimulates successive regions to contract by reflex action, producing a peristaltic wave.

Food undergoes no change in the oesophagus forcing the food into the stomach by peristalsis. The cardiac sphincter opens as food enters the stomach and then closes again to check the food passing back into the oesophagus. The food is hardly present for 2 to 3 seconds in the oesophagus. The cardiac sphincter is much more effective in infants so that regurgitation is much more common in them than in adults.

Note: Food does not merely slide down the oesophagus due to gravity, it is actively pushed along by peristalsis. This is shown by the fact that we can swallow while upside down on the head or even on the moon. In a grazing horse, food moves up the neck against gravity.