We assume the major function of the arterial system is transporting energy via its transverse vibration to facilitate the blood flowing all the way down to the microcirculation. A highly efficient system is related to maintaining a large pressure pulse along the artery for a given ventricular power. The arterial system is described as a composition of many infinitesimal Windkessels. The strong tethering in the longitudinal direction connects all the Windkessels together and makes them vibrate in coupled modes. It was assumed that at rest condition, the arterial system is in a steady distributed oscillatory state, which is the superposition of many harmonic modes of the transverse vibration in the arterial wall and the adherent blood. Every vibration mode has its own characteristic frequency, which depends on the geometry, the mass density, the elasticity, and the tethering of the arterial system. If the heart rate is near the fundamental natural frequency, the system is in a good resonance condition, we call this "frequency matching." In this condition, the pulsatile pressure wave is maximized. A pressure wave equation derived previously was used to predict this fundamental frequency. The theoretical result gave that heart rate is proportional to the average high-frequency phase velocity of the pressure wave and the inverse of the animal body length dimension. The area compliance related to the efficiency of the circulatory system is also mentioned.

Acupuncture points (acupoints) form part of the meridian system that constitutes the most fundamental concept in oriental medicine, but their physiological basis has not been clarified. In this study we employed laser Doppler flowmetry (LDF) to extract the microcirculatory characteristics of acupoints and their surrounding tissues, and we interpreted the results from the viewpoint of microcirculatory physiology. Three groups of measurements were performed focusing on the following two important acupoints in oriental medicine in healthy volunteers (n = 13 for group A and n = 9 for groups B and C, respectively): Hoh-Ku (Li4, on the hand) and Ching-Ku (B64, on the foot). The two groups of measurements around Hoh-Ku (Groups A and B) were so designed as to examine the effect of the direction of the nonacupoint away from the acupoint, whereas comparison between the Hoh-Ku and the Ching-Ku measurements was to verify whether the phenomenon was consistent in the upper and the lower extremities. We found that the mean LDF signals were significantly larger at the acupoints than in their surrounding tissues (all p < 0.05), which indicates a larger blood supply into the microvascular beds of acupoints. The results indicate that the physical properties of the vascular structure of acupoints may affect the perfusion resistance, and thereby modulate the microcirculatory perfusion in accordance with tissue needs. This finding facilitates the localization of acupoints, helps in identifying the connection between microcirculatory physiology and responses to acupoint stimulation, and introduces an objective research method for understanding the mechanisms that underlie oriental medicine.

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