Anatomy And Physiology

Anatomy Physiology

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The human body has one of the most complicated and effective buffer systems ever known to the mankind and collectively, these systems are responsible for maintaining human life. In general, a buffer is a solution that contains substances which has the ability to minimize changes in the pH when acids or bases are added to the solution. Likewise, the human body contains intracellular and extracellular spaces filled with fluids which are maintained within a fixed pH range with the  support from several buffer systems. This article shall describe briefly some of the main buffer systems in the body, along with how these systems interact to provide a delicate balance at all tissue levels.

Overall, the body is comprised of three main buffers. These are the bicarbonate buffer system, the protein buffer system and the phosphate buffer system.

Bicarbonate buffer system

Among the three buffer systems, bicarbonate the buffer system is the most important in relation to maintaining the pH of extracellular fluids. Therefore, it is the most important buffer system when it comes to dowsing the metabolic acids although it is not much useful in regulating the acid changes that take place due to respiratory acid-base disorders. The bicarbonate buffer system is also responsible for regulating the acid base balance in the stomach and neutralizing the acidity of stomach content as it reaches the small intestine. Although the bicarbonate system is smaller in capacity when compared with other buffer systems, it is the most useful in relation to eliminating most of the acid wastes over a long period of time. The reason for this is its ability to continuously eliminate CO2 and H+ from the tissues and blood, eliminate H+ and CO2 in the lungs as well as eliminate H+ in the kidneys.

Protein buffer system

While bicarbonate buffer system accounts for most of the buffering in the extra-cellular compartment, protein buffer system contributes mainly to the intra-cellular buffering although it exerts extra-cellular buffering as well. As such, protein buffer system is also known as ‘cellular buffering’. Among the intracellular protein buffers, hemoglobin is the main contributor while plasma proteins are the main sources of extracellular protein buffering. However, the buffering capacity of hemoglobin is around 6 times more than the buffering capacity of the plasma proteins. In addition, the deoxy form of hemoglobin is far more effective than its saturated oxyhemoglobin.

Phosphate buffer system

Phosphate buffer system is a relatively unimportant buffer system when it comes to buffering the pH changes in the blood due to its low concentration of hydrogen phosphate and dihydrogen phosphate ions. However, when it comes to intracellular compartment and urine, the concentration of these two ions would be rather high and therefore its buffering capacity would also be at a higher level. The importance of phosphate buffer system can be illustrated with regard to the buffering action of urine. Thus, the phosphates promote holding of H+ in the urine and thereby eliminating the same via urine. At the same time, because of the phosphate effect, the kidneys are able to absorb the bicarbonates back into the body without dragging the H+ back in to the system. This allows the body to maintain a acid base balance, even in instances where the body produce higher concentration of H+ due to various reasons.

Thus, when looking at these three systems, it is obvious that unless all these systems function properly, it is difficult to maintain the pH balance and therefore the effectiveness of cellular functioning. 

More about this author: Dr Pandula Siribaddana

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