A stent graft system includes a plurality of stents that are configured to be assembled in situ to provide an aortal stent graft assembly. The system may include a tubular segment that is configured to engage healthy aortic tissue, a plurality of segments configured to sealingly engage the tubular segment and comprising one or a plurality of vents or side channels that are oriented proximally and are configured to receive and seal with smaller-diameter stent grafts. In some embodiments, the system further includes a tubular segment having a bifurcated distal end. For example, the system may be assembled to provide a flow channel and support structure for stent grafts that engage one or more of the right and left iliac arteries, the celiac artery, the superior mesenteric artery, and the renal arteries.
