Unloaded dimensions and in vivo (IV) axial stretch ratio of the ascending aorta in WT and Fbln5−/− mice throughout early maturation. The outer diameter and thickness were measured from cut rings of arterial sections after mechanical testing, whereas the length and stretch ratio were measured from images of the aorta before and after dissection. Data are presented as mean ± s.e.m. N = 8–13 for each group.