This is a contiguous series of axial CT slices of the pelvis in a 41y old man. Intravascular contrast has been administered to the patient, and oral contrast has been swallowed by him. 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 slices and try to identify the labelled structures. Sometimes a structure is labelled in only one of the sections in which it can be seen; in other cases the same structure may be labelled 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.