Ovarian artery. Coloured scanning electron micrograph (SEM) of an ovarian artery that has been freeze-fractured to show internal details. An ovarian artery is a blood vessel that supplies oxygenated blood to the ovary. In cross-section the endothelium (tunica intima) can be seen in red, comprising of specialised epithelial cells that line the circulatory system. Surrounding this layer is the tunica media (brown), which is made up of smooth muscle cells and elastic tissue. The outermost layer (green), which surrounds the tunica media, is called the tunica externa, and is mainly composed of collagen. This collagen anchors the blood vessels to nearby organs, providing stability. Magnification: x780 when printed 10 centimetres wide.