Blood vessel. Coloured scanning electron micrograph (SEM) of a blood vessel (arteriole) in the dermis of the skin. In the blood vessel are red blood cells (erythrocytes, red) which carry oxygen around the body. the blood vessel endothelium is covered in microvilli. The blood vessel is surrounded by connective tissue which gives the skin its tone and elasticity (not vissible). Magnification: 1000 when printed at 10 centimetres wide.