24.3 MB (2.1 MB compressed)
3425 x 2478 pixels
29.0 x 21.1 cm ⏐ 11.4 x 8.3 in (300dpi)
PHOTO INSOLITE REALITE / SCIENCE PHOTO LIBRARY PHOTO INSOLITE REALITE / SCIENCE PHOTO LIBRARY
False-colour scanning electron micrograph (SEM) of a mass of human blood platelets (thrombocytes). Platelets are small, non-nucleated cells formed in the bone marrow, and are present in circulating blood in large numbers. Their shape in an unactivated state is round or oval (2-3 micrometres diameter); activated platelets have dendritic processes, or pseudopodia. Platelets function in 2 ways. Firstly, they help plug defects in the walls of small blood vessels: secondly, they are involved in clotting & also release serotonin, which reduces blood flow by constricting damaged vessels. Magnification: x2,000 at 6x7cm, x1000 at 35mm size.
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