Positional variations in fracture toughness, stiffness and strength of descending thoracic pig aorta.

The tunica media and intima of descending thoracic aortas from commercially killed pigs showed variations in mechanical properties along their length in a region extending from just in front of the first intercostal artery to the sixth intercostal artery. Along this region circumferential toughness, measured as work of fracture from a tear test, increased, longitudinal and circumferential ultimate tensile strength increased and longitudinal and circumferential stress-strain gradients of excised strips increased further away from the heart. These increasing mechanical properties are positively correlated with an increase in collagen mass fraction and an increase of radius/thickness ratio away from the heart over this region.