HATTIE YOUNG / SCIENCE PHOTO LIBRARY HATTIE YOUNG / SCIENCE PHOTO LIBRARY
A nurse draws a blood sample from the arm of an elderly woman, in order to carry out a liver function test. A tourniquet (strap) is used to restrict the flow of blood in the vein. This blood sample will be chemically tested for elec- trolytes and levels of urea. It will help diagnose liver disease, inflammation, and the efficiency of the liver to filter and cleanse the blood of toxic substances.
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