Ruptured capillary. Coloured scanning electron micrograph (SEM) of a red blood cell squeezing out of a torn capillary. A capillary is the smallest type of blood vessel, often only just large enough for red blood cells to pass through. Red blood cells (erythrocytes) are biconcave, disc-shaped cells that transport oxygen from the lungs to body cells.
STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY Blood clot. Coloured scanning electron micrograph (SEM) of red blood cells (erythrocytes, red) clumped together with fibrin (brown) to form a blood clot. Magnification: x5000.