Disclosed herein are systems and methods for sequentially dilating a vessel, where a guidewire extends into the vessel through a tissue opening in a tissue surface. The method can comprise advancing a dilator assembly over a portion of the guidewire that is exterior to the tissue opening; extending a first dilator segment from the dilator assembly; advancing at least the first dilator segment into the tissue opening to dilate the vessel while the first dilator segment remains extended from the dilator assembly; extending a second dilator segment from the dilator assembly, where the first dilator segment remains coupled to the second dilator segment and partially extends from the second dilator segment; advancing the first dilator segment and the second dilator segment into the tissue opening to further sequentially dilate the vessel while the second dilator segment remains extended from the dilator assembly.