STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY
White blood cells & platelets. Coloured scanning electron micrograph (SEM) of a group of white blood cells (leucocytes) and activated platelets in human blood. The larger rounded white blood cells (coloured pink, light blue) play a role in the body's immune response. At centre and far left are smaller platelets (thrombocytes, dark blue). Platelets are non-nucleated cells found in large numbers in the blood. When inactive they are round or oval discs; activated they have dendritic processes, or pseudopodia (as seen here), and they may become star-shaped. When activated, platelets clump together and are involved in blood clotting. Magnification: unknown.
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