Blood vessel. Coloured transmission electron micrograph (TEM) of a section through a blood vessel in the spinal cord. There are red blood cells (erythrocytes, dark red) in the vessel's lumen (interior). The nuclei of the endothelial cells that form the blood vessel's inner lining are green. Blood vessels carry oxygen, nutrients and hormones around the body. This blood vessel is in the white matter of the spinal cord. White matter consists of axons (yellow), the fibres that carry nerve signals away from each neurone (nerve cell), wrapped in myelin (green). Magnification: x600 at 6x7cm size. x2000 at 7.5x9.5."