Caption

Blood clot. Coloured Scanning Electron Micrograph (SEM) of red blood cells enmeshed in a web of fibrin strands in clotting blood. Blood clots form when tissue damage, turbulence or chemical factors trigger the conversion of the soluble protein fibrinogen into insoluble fibres of fibrin. The fibres trap blood cells forming a solid clot, sealing the wound. The clot helps prevent loss of blood and infection of the wound by foreign agents such as bacteria. Red blood cells are the most abundant cells in the blood. They contain the protein haemoglobin, which picks up oxygen in the lungs and releases it around the body. Magnification: x1430 at 6x7cm size.