Most computations of arterial mechanics treat the wall as a mechanically ho
mogeneous body, bur then are no data to support or refute this. To evaluate
this assumption, experiments were performed that measured the deformation
of 4 elastic lamellae located at 4 equidistant points across the thickness
of the media. Data were obtained at 25-mm Hg pressure steps between 0 and 2
00 mm Hg. To satisfy the constraints of incompassibility in an isovolumetri
c cylinder, the innermost structures must undergo larger deformations than
the outermost structures. This manifests as thinning of the wall. Therefore
, each experiment was performed twice: once with a vessel segment in its no
rmal cylindrical configuration, and again with a contiguous vessel segment
turned inside-out to form an inverted cylinder. The deformations of individ
ual lamellae obtained in normal and inverted vessel segments were averaged
to determine their extensions independent of location. Results showed that
the extensibilities of the lamellae were equal at all 4 anatomic locations
across the media, suggesting equal stiffnesses of the lamellae, Other studi
es were performed to examine the distribution of the circumferential retrac
tions of the lamellae that occurs when a vessel is extended longitudinally.
Results showed that circumferential retraction also was distributed unifor
mly across the wall, These findings demonstrate that the elastic lamellae b
ehave uniformly in both the circumferential and longitudinal directions at
different locations across the wall thickness. Because of the interlocked s
tructure of the elastin, muscle, and collagen in the media, these findings
suggest that although the media is histologically heterogeneous, it acts me
chanically as a homogeneous material.