Hi pcb
the stomach is well able to withstand the stomach acid...Its part of its job, but the lining of the esophagus is not designed to handle the return of the acidic mixture of stomach contents which back up into it with reflux.
Remember that your stomach acid is more potent than battery acid and will damage the lining of the esophagus.
Imagine a valve at the bottom of your esophagus which lets food through to the stomach. This valve is called the lower esophagael sphincter (les)
normally this valve operates only one way, but when it is weak, it can allow food and acid from the stomach back up into the esophagus and your problems begin.
I write regularly on this topic on my site.
Acidrefluxheartburn.Com
good luck
tony