If the liquids we drink end up in the stomach, how does our stomach acid not get thinned down by the constant flow of liquid?
In: Biology
The first thing to realize is that it takes quite a lot of liquid to lower your stomach acid however it can create a problem if the stomach is not able to work the way it’s designed.
The solution is quite elegant and is based on the shape of your stomach. When your stomach is empty it is shaped similarly to a banana. To be able to expand many times its size to accommodate a big meal, there are deep folds which run the length of the stomach. When you drink a liquid, it spreads out quickly and runs into the deep crevices. This keeps the liquid separate from the solids and allows the liquids to be absorbed almost immediately. Only a few things can be absorbed this way: directly through the stomach wall; water, some sugars in solution, alcohol, some other smaller molecules that are in solution such as medications.
When you eat something with very little moisture, your stomach will need to add fluids to the contents so that the acidity can mix in thoroughly. Your stomach will not use the water you just drank directly but will take the fluid from your bloodstream to create the acidic juices.
Some problems that stop this system from working are:
Very cold liquids will slow down or even stop all stomach processes until the contents are warmed up by your bodies heat.
If your stomach is overfull then there will be no folds left to accommodate the fluids and they will sit on top and take much longer to absorb through a relatively small area of stomach wall that they are exposed to.
A few other interesting points:
The stomach does not usually reabsorb its own acid and the top of the stomach(where most water is absorbed) has less acidity than the bottom. Food is mixed with your stomach acid in the order that it is eaten. The first bite reaches your stomach’s exit first. This sphincter has special cells called parietal cells which register the acidity of the contents and will not open the gates until proper acidity is reached. Fibrous and water filled veggies take less stomach acid to reach the correct pH than dense proteins and concentrated fats. So a big steak can sit for a long time(around 2 hours) and block the passage of a salad sitting on top which would only take 20 minutes to go through if it was first. If the salad sits long enough without getting fully acidified, it will start to ferment and create burping and upward pressure. This will be increased when lying down and may cause stomach contents to be forced up the esophagus causing acid reflux.
The stomach itself does not get digested by the stomach acid due to a mucus lining that protects the stomach lining. Although this lining is very resistant to strong acid for short periods, even a weak acid can erode it over a long period. When stomach contents do not get thoroughly acidified, the parietal cells will not let the food through and it sits there long enough to erode the mucus lining. Many ulcers are caused this way- paradoxically from too little acid!
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