What moves a bolus of food from the mouth to stomach?

The movement of a bolus of food from the mouth to the stomach is facilitated by a series of coordinated muscle contractions and relaxations known as peristalsis. Peristalsis is a rhythmic, wave-like motion that propels the food bolus along the esophagus, the muscular tube connecting the mouth to the stomach.

Here's a step-by-step explanation of how peristalsis works:

1. Swallowing: When you swallow, the muscles in your tongue and cheeks push the food bolus toward the back of your throat.

2. Esophageal Sphincter Relaxation: The upper esophageal sphincter (UES), a circular muscle at the top of the esophagus, relaxes to allow the food bolus to enter the esophagus.

3. Peristaltic Waves: Once the food bolus enters the esophagus, the muscles in the esophageal walls contract and relax in a coordinated manner. These contractions create a wave-like motion that pushes the food bolus downward toward the stomach.

4. Esophageal Body Contractions: The circular muscles of the esophagus contract behind the food bolus, while the longitudinal muscles relax, effectively shortening the esophagus and propelling the bolus forward.

5. Lower Esophageal Sphincter Relaxation: As the food bolus reaches the end of the esophagus, the lower esophageal sphincter (LES), another circular muscle, relaxes to allow the bolus to enter the stomach.

6. Stomach Reception: Once the food bolus enters the stomach, it mixes with gastric juices and undergoes further digestion.

Peristalsis is a vital physiological process that ensures the efficient transport of food from the mouth to the stomach. It helps prevent food from getting stuck in the esophagus and allows for the proper digestion and absorption of nutrients.