The body’s line of defense against HCl: The esophagus, stomach, and small intestine each have their own mechanisms for protection against the dangerously low pH of stomach acid, whether keeping acid away from sensitive tissues or neutralizing acid already present.
*Peristalsis clears the esophagus by pushing stomach contents back into the stomach; gravity also aids this process.
Saliva naturally contains bicarbonate, a chemical that helps to neutralize acid in the digestive tract.
Layers of cells called *stratified squamous epithelium line the esophagus and keep acid from seeping in deep enough to do serious damage.
Mucous glands in the wall of the esophagus secrete a protective lubricant.
Mucus-secreting cells coat the entire surface of the stomach with a thick layer of mucus that has buffering, lubricating and antibacterial properties.
A high turnover rate to replace damaged cells allows surface mucous cells to renew themselves every 3-5 days.
Tight junctions (arrow) between the epithelial cellsact as a seal to prevent acid from seeping between the cells and into the stomach lining.
The parietal cell’s membrane is highly impermeable to acid, protecting the cell from acid degradation.
Pancreatic juices containing bicarbonate are secreted into the small intestine. This neutralizes much of the acid leaving the stomach.
Glands in the wall of the duodenum(first segment of the small intestine) also secrete bicarbonate.