Arterial reflecting sites
Every impedance mismatch along the arterial tree contributes to the reflected wave. However, the primary source for reflection is in the arterioles. The reflected waves from the many arterioles in the trunk and lower limbs coalesce to provide what appears to be a single reflected wave from an average or functionally discrete reflecting site.
Note that the reflected wave from the abdomen and lower limbs travels back to the the upper limbs.