55.3 MB (7.0 MB compressed)
5394 x 3584 pixels
45.7 x 30.2 cm ⏐ 18.0 x 11.9 in (300dpi)
NIBSC / SCIENCE PHOTO LIBRARY NIBSC / SCIENCE PHOTO LIBRARY
Scanning electron micrograph of an unactivated blood platelet. Platelets (thrombocytes) 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), as here; activated platelets have dendritic processes, or pseudopodia. Platelets function in 2 ways. Firstly, they help plug small defects in the walls of small blood vessels: secondly, they are involved in clotting & also release serotonin, which reduces blood flow by constricting the damaged vessels. Magnification: x53,000 at 8x10inch size.
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