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.
Blood clot. Coloured scanning electron micrograph (SEM) of a blood clot from the inner wall of the left ventricle of a human heart. Red blood cells (erythrocytes) are trapped within a fibrin protein mesh (cream). The fibrin mesh is formed in response to chemicals secreted by platelets (pink), fragments of white blood cells. Clots are formed in response to cardiovascular disease or injuries to blood vessels. Connective tissue (orange) is also seen.