This is a contiguous series of heart CT slices in a 42y old woman. Intravascular contrast was injected into the right median cubital vein. You can scan through the series either by (1) positioning the cursor over the image, holding down the left mouse button, then sliding the cursor up or down the image, or (2) hitting the keyboard keys > and < (no shift required). At the end of the series of axial sections are presented colorized volume rendered images depicting the coronary arteries in situ, and one that shows them in isolation. Scan through the series of CT slices and try to identify the structures to which lines are drawn. Sometimes a structure has a line drawn to it in only one of the sections in which it can be seen; in other cases the same structure may have lines drawn to it in a few sections, not necessarily contiguous. The answers will be revealed when you click on the appropriately labelled drop-down arrows below the image.