Artery, light micrograph. Full thickness of the wall of a muscular artery. Blood is seen in the lumen. The thick wavy line is the internal elastic lamina that becomes extended and circular in profile when the artery is dilated. The wall (tunica media) is comprised of layers of smooth muscle cells in a state of contraction with nuclei showing twisted or corkscrew shapes. The outer tissue is the tunica adventitia showing scattered fibroblasts and smooth muscle cells with strands of elastic fibres. Epoxy resin section. Toluidine blue stain. Magnification: x900 when printed at 10cm.