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Liver blood vessels. Coloured 3-D ultrasound scan of blood vessels in a human liver. The liver breaks down the body's harmful waste products, destroys old red blood cells, and produces bile and some proteins. Blood flows into the liver through the hepatic artery and the portal vein. The portal vein carries blood from the digestive system and spleen. Blood is carried away to the heart by the inferior vena cava. Ultrasound is a diagnostic technique that sends high-frequency sound waves into the body via a transducer. The returning echoes are recorded and used to build an image of an internal structure. Minimal rendering was used to improve the image resolution. (KEYSTONE/SCIENCE PHOTO LIBRARY/DR NAJEEB LAYYOUS)