SIGRID GOMBERT / SCIENCE PHOTO LIBRARY SIGRID GOMBERT / SCIENCE PHOTO LIBRARY
Red blood cells in a blood vessel. Coloured scanning electron micrograph (SEM) of human red blood cells (erythrocytes) in a blood vessel. Red blood cells are biconcave, giving them a large surface area for gas exchange, and highly elastic, enabling them to pass through narrow capillary vessels. The main function of red blood cells is to distribute oxygen to body tissues and to carry waste carbon dioxide back to the lungs.
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