Red blood cells, white blood cells and platelets, SEM

Human red blood cells, monocyte (green), neutrophil (purple), T lymphocyte (blue) - white blood cells, and activated platelets (brown), coloured scanning electron micrograph (SEM). Red blood cells (RBCs), or erythrocytes, are involved in delivering oxygen to the body tissue. Monocytes are a type of white blood cell (leukocyte) and part of the innate immune system. T lymphocytes circulate in the blood before migrating to the thymus where they develop into specialized cells that are able to identify antigens and infected tissue cells. Neutrophils assist in cellular defence (phagocytosis) of pathogenic microorganisms. Platelets are blood cell fragments that play an essential role in blood clotting and wound repair. When an injury such as a cut is sustained, platelets change their shape (now known as activated platelets), become sticky and build up on a vessel wall to form a plug. Magnification: x500 when shortest axis printed at 25