Bodily Defenses Image Map

Liver Functions

Observing the liver tells us a lot about its function:

  • huge veins come into the liver from the gut
  • venous blood flows past single rows of liver cells
  • blood takes about 8 seconds to pass by the liver cells
  • the flow path exposes blood to many phagocytotic, cells

Comparing the chemical contents of the blood coming in with that of the blood leaving the liver shows that the liver must:

  • make urea, a protein waste product
  • make bile, which is released from the gall bladder to the intestines (makes fat easier to digest)
  • remove low density lipids (LDL) and add high density lipids (HDL) to blood, thus protecting against hardening of the arteries
  • convert and detoxify many drugs and toxins
Medical Application - Liver Function Tests

Because the liver is so vital for life, it is important to know if the liver is working normally. This is especially true in older age, when the liver is most likely to be damaged. There are several laboratory tests that doctors can have performed to check if liver function is normal.

Certain laboratory tests are used to determine whether the function of your liver is normal. Any symptoms of illness that might occur because of a poorly functioning liver will prompt a physician to consider ordering a medical laboratory to perform certain liver function tests on a blood sample. Such symptoms could include a yellowing of skin and membranes of the eye (called jaundice), a prolonged bleeding after cuts and bruises, and swollen or hardness of the liver (which the doctor determines by pressing on your abdomen over the liver). Unfortunately, you can have severe liver damage long before obvious symptoms appear. Sometimes, even the laboratory tests fail to detect severe liver damage.

The lab tests look for:

  • Certain enzymes - these leak from damaged liver cells into the blood
  • Bilirubin (a normal by-product of red blood cell turnover) - builds up when liver is too damaged to remove it. This appears as jaundice.    
  • Albumin (this protein is made in the liver) - decreases in liver damage
  • Blood clotting proteins (these are made in the liver) - clotting time is prolonged when liver is damaged

Many prescription drugs can damage the liver in the process of being deactivated by liver cells. But the most common causes of liver damage are alcohol abuse and certain virus infections (viral hepatitis).



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