The human body requires a balance between acids and bases to function properly. The pH level is a measurement of the acid-base relationship. It is actually the number of hydrogen ions in a particular solution. As the number of hydrogen ions increases, the pH level decreases. Low pH levels, or those under seven, are considered acidic, with higher pH levels, from seven to 14, called basic, or alkaline. It is vital for the body to have the proper pH needed for certain chemical reactions. Three internal mechanisms--buffers, respirations and kidney function--assist in regulating pH.
Normal Levels
The ideal pH for blood is between 7.35 and 7.45. Even a minor deviation from this range can cause problems with many body organs. Urine has a larger normal range, with its normal pH being between five and eight. Intestinal contents are more alkaline and usually have a pH that falls between eight and 10.
Buffers
Buffers are the combinations of the body's own weak bases and acids, which exist in normal pH conditions. They work to minimize pH changes by adjusting the proportions of the acids and bases. Buffers work in pairs, with each part able to act in certain situations. If there is not enough hydrogen present, and the body is too basic, buffers will give hydrogen ions to the balance. If the concentration of hydrogen ions is high, the buffer will take some of the hydrogen ions out. Using this two-part system, buffers are an effective defense against pH imbalances.
Respiration
Breathing plays another role in the maintenance of the body's pH range. Respiration allows carbon dioxide to leave the body. Carbon dioxide is slightly acidic. As carbon dioxide builds up in the blood, the acidity of the blood increases. The brain then regulates breathing, by adjusting the depth and speed, to balance the pH. This adjustment can occur at any time as needed.
Kidney Function
The kidneys are another line of defense against pH imbalances in the body. They are able to adjust the amount of acid or base that is excreted by the body in the urine. The kidneys work much more slowly than the lungs do, however, so results are not seen as quickly.
Imbalances
Acidosis and alkalosis, acid-base imbalances of the body, can be life-threatening. When an imbalance is present, body systems cannot function properly. This may lead to problems with breathing and circulation, sometimes resulting in coma or death. Acidosis occurs when the blood pH is too low (under 7.35), and alkalosis occurs when the pH is higher than 7.45. Depending on the cause, these disorders are considered metabolic or respiratory. Respiratory disorders are caused by abnormalities in carbon dioxide excretion, typically due to lung disorders. Metabolic conditions are caused by an imbalance in the excretion of acids and bases by the kidneys. To rectify these dangerous situations, medications are usually given to restore the acid-base balance.
References
- The Human Body in Health and Illness; Barbara Herlihy, PhD, RN; 2003
- The Physiology Coloring Book; Robert I. Macey; 2000
- The Merck Manual
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