A healthy artery is wider and has no blockages. The lumen (which is the hole in the centre of the artery), is open and clear. This means there is more blood flow. An artery of a person suffering from coronary heart disease is often blocked, usually by a fatty deposit. This means the blood does not flow as well. (See diagram, in which I would draw two arteries, one with a blockage of fatty deposit, one clear and healthy).
Mitosis is the phase of the cell cycle where the nucleus of a cell is divided into two nuclei with an equal amount of genetic material in both the daughter nuclei. It succeeds the G2 phase and is succeeded by cytoplasmic division after the separation of the nucleus.