STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY
Human blood cells. Coloured scanning electron micrograph (SEM) of four platelets (thrombocytes, yellow), a red blood cell (erythrocyte, red) & two white blood cells (leucocytes, blue and purple). Platelets are produced in the bone marrow, they are involved in the process of blood clotting. Red blood cells carry oxygen from the lungs to all the cells of the body, and carbon dioxide from these cells back to the lungs. White blood cells are involved with the human immune system. Lymphocytes (blue) recognise foreign antigens and destroy invaders, neutrophils (purple) engulf bacteria and release an antibacterial enzyme (lysozyme). Magnification: x4250 at 6x7cm size.
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