pH is a measure of how acidic a water-based solution is. Since our bodies are mostly water, pH can be used to describe how much acid is in the fluids in our bodies.
Water has a pH of 7.0. pHs lower than 7 are acidic; pHs above 7 are basic, or alkaline.
Our bodies maintain our blood at a pH of about 7.4. The kidneys tightly regulate this pH balance by continuously filtering the acids and bases in the blood. The kidneys excrete just the right amount of acid or base in the urine to keep the system in pH balance.
Certain other body fluids are highly acidic (like stomach acid) or basic (enzyme-rich fluids in the pancreas). These fluids are kept tightly walled off from the blood and body tissues, where they could cause damage if released inappropriately.
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