The in situ longitudinal strain of canine and porcine aortas was inves
tigated. Marks of black water-resistant ink were placed on the aortas
and the axial lengths between the marks were measured in situ and in v
itro. When the aortas were cut, the retraction was measured and descri
bed by the stretch ratio, which is defined as the length of a segment
in situ divided by the length at no-load state. Results show that the
stretch ratios of both porcine and canine aortas increase monotonicall
y from 1.2 in the descending region to about 1.5 in abdominal region.
Species differences are seen in the middle region. In both animals, th
e stretch ratio is correlated to the cross-sectional area of the vesse
l wall.