What mechanisms prevent gastric reflux into the esophagus when lying down or bending over?

Answer 1

Gastro oesophageal reflux is a condition where the acidic content of the stomach regurgitates back into the oesophagus. The distal oesophageal mucosa is non glandular in type (it is squamous epithelium), therefore, it can easily be damaged by chronic acid reflux.

To prevent this, there are several mechanisms in place:

1. The lower oesophageal sphincter (LOS) is tonically active but relaxes on swallowing. The tonic activity of the LOS between meals prevents reflux of gastric contents into the oesophagus.
2. The prominent smooth muscle of the lower oesophagus acts as a internal phincter to prevent reflux.
3. The right crus of the diaphragm which surrounds the oesophagus exerts a pinch-cock like action on the oesophagus to prevent reflux (external sphincter).
4. The oblique or sling fibers of the stomach wall create a flap valve that helps close off the esophagogastric junction and prevent regurgitation when intragastric pressure rises.
5. Another factor that helps to prevent reflux is a valvelike mechanism of a short portion of the esophagus that extends slightly into the stomach. Increased intra-abdominal pressure caves the esophagus inward at this point. Thus, this valvelike closure of the lower esophagus helps to prevent high intra-abdominal pressure from forcing stomach contents backward into the esophagus.

Answer 2

The lower esophageal sphincter is the mechanism that normally prevents gastric reflux into the esophagus when lying down or bending over. It is located between the esophagus and the stomach.