A, B: The left and accessory (Acc.) primary branch lengths measured on Tree Surveyor are significantly shorter in Admats18−/− lungs compared to somite-matched Adamts18+/− and wildtype lungs (n = 5, somite range = 49–51). C, D: The lengths of the highlighted branch segments (L1, L2, A1) divided by the total length of the primary branch associated with each segment quantifies the primary branch segment proportion. There is no significant difference in segment proportion within the left branch for segments L1 and L2. There is a significant difference between Adamts18−/− and wildtype proportion for A1. Error bars are SD and significance was determined by a two-tailed t-test. * = p ≤ 0.05, ** = p ≤ 0.01, *** = p ≤ 0.001. Line = 200μm.