Hemodynamics of the omphalo-mesenteric arteries in stage 18 chicken embryos and "flow-structure" relations for the microcirculation.

OBJECTIVE

The primary objective of this study is to evaluate the hemodynamic and structural characteristics of the omphalo-mesenteric (vitelline) arteries in stage 18 chicken embryos. The measured results were compared with Murray's law to validate the theoretical prediction on the vascular structure.

METHODS

Variation of hemodynamic parameters such as mean velocity (U(mean)), peak velocity (U(peak)) at the systolic phase, velocity fluctuations (U(fluc)) at the pulsatile frequency, and the Womersley number (Ω) were measured with respect to the geometric parameters including the bifurcation cascade level (BCL), vessel diameter (D), and distance (L) from the first bifurcation. They were assessed by using the time-resolved in vivo micro-PIV (particle image velocimetry) technique and the geometric information was obtained from the microscopic vessel images.

RESULTS

The effect of "branching of the vessel" on the variation of hemodynamic characteristics is similar to those of the "increase in distance" from the first bifurcation and the "decrease in vessel diameter". The flow quantities (U(mean), U(peak) and U(fluc)) decrease due to the increase in cross-sectional area ratio (γ=1.209=(∑D(daughter)(2))/D(mother)(2)), and the Womersley number also decreases as the bifurcation cascades (Ω«1).

CONCLUSION

The geometric parameters are closely related to the variation of hemodynamic characteristics. Murray's law with non-constant viscosity hypothesis would provide an insight on the two-phase nature of microvascular blood flows.