Vessel Wall

As blood pulses in an artery, its wall alternatively stretches and recoils. S. Hales described in 1733 blood systolic storage and diastolic restitution. O. Frank in 1899 modeled arterial capacitance by a windkessel element, i.e., a damping air chamber incorporated in a rigid pipe network. Blood vessels are pressure and volume buffers. Veins, which are the major blood storage compartments, accommodate volume changes by shrinking to possible collapse.

Wall expansion and relaxation depend on the rheological properties of the vessel wall, and thus to its composition and structure. In particular, distension and subsequent recoil are achieved by the architecture and interactions between coupled elastin and collagen fibers. In addition to passive caliber changes, the vessel wall undergoes active variations due to vasomotor tone. Vascular smooth muscle activity fits the blood flow to the tissue requirements.