This is a contiguous series of sagittal MRA (magnetic resonance angiography) images of the chest in a 14y old boy. The first image is furthest to the left; subsequent images progress toward the patient's right side. 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). Scan through this series of MRA 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.