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Elementary Science Education

Part 4. The role of the liver

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      Bernard Nebel

      An overview of liver functions may be found by typing,  What does the liver do? Emma Bryce – you tube, into your browser.

      The following may be helpful.

      By weight, the liver is the largest) organ in the body. It is part of the digestive system, but what does it do? 

      Have kids consider discrepancies between requirements of our body’s cells and when and what we eat. Two major dicrepancies are the following: 

      • Cells need a continuous supply of glucose (24-7) just to maintain a living state. Muscle cells need large amounts of glucose when we are physically active, much less when we are inactive. Conspicuously, the times and amounts we eat do not correspond our cell’s requirements. 

      • Our cells require certain kinds and amounts of given amino acids to make their proteins (enzymes and structural parts). The amino acids that come from the digestion of protein in our food has differs kinds and amounts.    

      Major functions of the liver are in resolving these disconnects. We have previously learned (lesson B-15) that capillaries in all tissues of the body converge into veins that lead back to the heart and lungs before making another circuit. Blood does not flow tissue to tissue or organ to organ. 

      There is one exception to this rule. Blood leaving the capillaries of the stomach and intestines converges into a vein that goes to the liver, ramifies again into capillaries throughout the liver. Only then does blood converge into the vein back to the heart. As this blood passes through the liver, these discrepancies are resolved. 

      •. Excess glucose, after eating, is taken from the blood and stored (as starch) in liver cells. Between meals, the reverse occurs.

      • Excess amino acids are stripped of the nitrogen which is then synthesized into urea and later excreted by the kidneys as urine. The carbon portion of amino acids is synthesized into glucose.
      • Excess glucose is converted to compounds that are synthesized into and put into long-term storage as body fat. The reverse occurs in times of need.
      • Other amino acids are interconverted into what the body’s cells require. (The exception is “essential amino acids”, a group of nine amino acids that our bodies cannot synthesize and therefore must be present in the diet. 

      Additional functions of the liver include:

      • Poisonous substances, e.g, alcohol, is cleared from the blood. Otherwise people would remain drunk indefinitely.
      • the liver stores iron required continuously in the replacement of blood.
      • The liver produces bile which is secreted into the intestine for the digestion of fats. 
      • The list goes on. More than 500 vital liver functions have been identified.

      Further information can be found at:

      By the way, there is a separate network of blood vessels from the heart to the liver, through capillaries, and back, that nourishes the liver cells themselves with glucose and oxygen to keep them able to do their multitude of jobs. 

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