STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY
Blood cells. Coloured scanning electron micrograph (SEM) of red blood cells (erythrocytes, red) and a white blood cell (leukocyte, grey). Some fibres of fibrin (yellow), a protein that functions in blood clotting, are also seen. The disc-shaped, biconcave erythrocytes transport oxygen to the body's cells and remove carbon dioxide to the lungs. Leukocytes are part of the immune system, defending the body against infection by ingesting pathogens by phagocytosis or by producing antibodies. Magnification: x4670 when printed 10cm wide.
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