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RESEARCH PAPERS

Active Contractions of Ureteral Segments

[+] Author and Article Information
P. F. Zupkas

Shiley, Inc., Irvine, Calif. 92714

Y. C. Fung

AMES/Bioengineering, University of California, San Diego, La Jolla, Calif. 92093

J Biomech Eng 107(1), 62-67 (Feb 01, 1985) (6 pages) doi:10.1115/1.3138522 History: Received August 08, 1983; Revised August 01, 1984; Online June 15, 2009

Abstract

The first step in the analysis of the biomechanics of any organ is to obtain its constitutive equation. In pursuit of a constitutive equation describing the peristalsis of the ureter, we measured the relationship between the length of the muscle, the velocity of contraction, and the active tension development of isolated ureter segments. The results of length-tension measurements (giving the maximum tension developed in isometric contraction of a ureter segment of specific length) were similar to those obtained by previous investigators and reflected the behavior of length-tension relationships for other smooth muscles. Two aspects of the force-velocity relationship of the ureter were examined: the effect of releasing the ureter at different times after stimulation, and that at different levels of afterload. Measurements were analyzed using the hyperbolic Hill’s equation in the form

T/T0 = (1 − v/v0)(1 + cv/v0)−1
where v is the velocity of contraction, v 0 is the velocity of contraction when T = 0, T is the tension in the muscle after release, T 0 is the tension in the muscle immediately prior to c is the dimensionless constant. The results of force-velocity measurements showed that the so-called “maximum” velocity v 0 , is the largest if the tension is released at a time of contraction, early in the rise portion of the contraction cycle. Further, if tension is released from an isometric contraction at a fixed time in the rise portion of the contraction cycle, the largest value of v 0 is obtained when the muscle length is in the range of 0.85–0.90 L max . Interestingly, the in vivo length of the ureter lies also in this range, 0.85–0.90 L max .

Copyright © 1985 by ASME
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