The stomach usually has a pH of 2 or 3.
That’s still really acidic. The stomach is
protected by having a layer of mucus between the
inside the stomach and the actual stomach tissue.
Some of the cells that line the stomach also make
a buffer (a high-pH liquid) that helps to keep the
pH right by the cells closer to neutral.
When there is nothing in the stomach, less
acid is produced.
This may seem like a waste of energy and
materials, creating a low pH, then trying to
protect itself. The acidic environment of the
stomach is important, though. Not only does
it help to break down certain foods, it kills
germs before they enter the small intestine.
The lining of the small intestine is more delicate
so that nutrients can be absorbed there.
The small intestine stays close to neutral because
the pancreas dumps a lot of buffers in right where
the stomach connects to the small intestine. This
pH is much closer to water and does not damage the
Why do you think the digestive system has zones
that are so different from each other?
You may want to explore a career in physiology or
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