Skin blood vessels. Coloured scanning electron micrograph (SEM) of two small blood vessels (lower left and upper right) in the dermis of the skin. The dermis is the layer of the skin which contains blood vessels, sweat glands and hair follicles. The blood vessels are seen to contain red blood cells (red), which are responsible for carrying oxygen around the body to tissues which require it. Some white blood cells (round, green) are seen in the tissue surrounding the blood vessel at lower left. These cells help clear the body of infection. The area surrounding the blood vessels is largely connective tissue, which gives the skin its tone and elasticity. Magnification unknown.