George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA.
Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu, Taiwan.
Neurourol Urodyn. 2023 Aug;42(6):1245-1254. doi: 10.1002/nau.25186. Epub 2023 May 16.
This study investigates how lumen roughness and urethral length influence urinary flow speed.
We used micro-computed tomography scans to measure the lumen roughness and dimensions for rabbits, cats, and pigs. We designed and fabricated three-dimensional-printed urethra mimics of varying roughness and length to perform flow experiments. We also developed a corresponding mathematical model to rationalize the observed flow speed.
We update the previously reported relationship between body mass and urethra length and diameter, now including 41 measurements for urethra length and 10 measurements for diameter. We report the relationship between lumen diameter and roughness as a function of position down the urethra for rabbits, cats, and pigs. The time course of urinary speed from our mimics is reported, as well as the average speed as a function of urethra length.
Based on the behavior of our mimics, we conclude that the lumen roughness in mammals reduces flow speed by up to 25% compared to smooth urethras. Urine flows fastest when the urethra length exceeds 25 times its diameter. Longer urethras do not drain faster due to viscous effects counteracting the additional gravitational head. However, flows with our urethra mimics are still 6 times faster than those observed in nature, suggesting that further work is needed to understand flow resistance in the urethra.
本研究旨在探讨管腔粗糙度和尿道长度如何影响尿流速度。
我们使用微计算机断层扫描测量了兔子、猫和猪的管腔粗糙度和尺寸。我们设计并制造了具有不同粗糙度和长度的三维打印尿道模拟物来进行流动实验。我们还开发了相应的数学模型来合理化观察到的流速。
我们更新了之前关于体重和尿道长度和直径的关系，现在包括 41 个尿道长度测量值和 10 个直径测量值。我们报告了兔子、猫和猪的尿道管腔直径和粗糙度随位置变化的关系。我们还报告了我们的模拟物的尿流速度随时间的变化情况，以及尿道长度对平均速度的影响。
根据我们的模拟物的行为，我们得出结论，哺乳动物的管腔粗糙度使流速降低了 25%，与光滑尿道相比。当尿道长度超过直径的 25 倍时，尿液流速最快。由于粘性效应抵消了额外的重力头，较长的尿道不会更快地排出尿液。然而，我们的尿道模拟物的流量仍然比自然界中观察到的流量快 6 倍，这表明需要进一步研究来理解尿道中的流动阻力。
