The arterial tissue consists of elastin and collagen which develop passive stresses in the arterial wall, and muscle cells that develop active stresses when are appropriately stimulated. Earlier model for the active properties of the arterial wall, where the muscle cells orientation is assumed circumferential, failed in describing accurately the tissue response to inflation-extension loading. It has been hypothesized that the development of active stresses in both circumferential and longitudinal directions could overcome this shortcoming.
Inflation-extension tests on common carotids of rabbits were performed with the muscle cells being either fully relaxed or fully contracted. Biomechanical model for the active properties of the arterial wall was developed, accounting for angular orientation of the muscle cells on the circumferential-longitudinal plane.
The biaxial constricting effect of the muscle cells was shown to characterize more accurately the active properties of the arterial wall compared to the model with only circumferential contribution.