MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I.Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

SECTION 4. BLOOD SYSTEM

PHYSICOCHEMICAL PROPERTIES OF BLOOD

2.BLOOD REACTION

The Blood reaction (pH) is determined by The ratio of hydrogen and hydroxyl ions it contains. In a neutral environment, the pH is 7.0, in an acidic environment, it is less than 7.0, and in an alkaline environment, it is greater than 7.0. The blood reaction is slightly alkaline. In arterial blood, the pH is 7.4, while in venous blood, it is 7.36. The Homeostasis of blood pH is strictly regulated. Life is possible only within a narrow pH range, specifically from 7.0 to 7.8. If these fluctuations exceed this range, Cellular METABOLISM is disrupted because Enzymes, which act as catalysts for biochemical reactions, can function only within a specific environmental pH.

However, in a healthy Organism, even with a significant intake of acids and alkalis into the blood, its reaction does not exceed normal limits. This is achieved through buffer systems that bind hydroxyl and hydrogen ions, thereby ensuring a constant pH. Buffer substances include Hemoglobin, bicarbonates, phosphates, and Proteins. The most powerful of these is the hemoglobin buffer.

The maintenance of a constant pH is facilitated by the functioning of the Lungs, Kidneys, Stomach, intestines, and Sweat Glands. Excess alkalis and acids are excreted via the kidneys and sweat glands.

During intense muscular exertion, large amounts of lactic acid are produced and enter the bloodstream. This leads to a shift in blood pH toward the acidic side. After the activity ceases, pH values return to normal. Certain diseases also cause a shift in blood pH toward the acidic side. A shift of blood pH toward an acidic environment is called acidosis, while a shift toward an alkaline environment is called alkalosis.

The blood reaction shifts toward the alkaline side during hyperventilation, when a significant amount of Carbon dioxide is eliminated from the blood.