Meeting Abstract

4.2  Friday, Jan. 4  Structure and Mechanics of Fin Whale Arteries LILLIE, MA*; PISCITELLI , MA; GOSLINE, JM; SHADWICK, RE; University of British Columbia; University of British Columbia; University of British Columbia; University of British Columbia lillie@zoology.ubc.ca

The mechanical properties of mammalian arteries are linked to their function and generally reflect the loads they experience in vivo. Fin whales have a collagen rich and unusually incompliant thoracic aorta. We hypothesized that it might represent a mechanism to deal with changing transmural arterial pressures, which may vary if thoracic pressure differs from ambient. To test this hypothesis we examined the morphology and the in vitro mechanical properties of a range of fin whale arteries exposed to both positive and negative transmural pressures. Arteries were tested under inflation for the pressure-stretch response and under deflation to determine the negative pressure required to cause buckling and collapse. We found abundant adventitial and perivascular collagen in all arteries. With the exception of the subclavian artery, the collagen became taut at very low pressures, stiffening the arteries circumferentially, allowing little compliance at low strains and stretches of only 10% at physiological pressures. Circumferential stiffness increased non-linearly with stretch. Under a negative transmural pressure some arteries collapsed readily while others did not, depending on their wall-thickness-to-radius ratio and on the stretch-dependent modulus. Wall bending was resisted by adventitial collagen, indicating a possible advantage of its recruitment at low stretches. However, adaptations to resist collapse under negative pressures and render diameter independent of pressure are of value only in a system where transmural arterial pressures vary. Whether these arterial properties provide evidence that transmural pressures do vary has yet to be established.