Duration of urination does not change with body size

摘要: Many urological studies rely on models of animals, such as rats and pigs, but their relation to the human urinary system is poorly understood. Here, we elucidate hydrodynamics urination across five orders magnitude in body mass. Using high-speed videography flow-rate measurement obtained at Zoo Atlanta, discover that all mammals above 3 kg weight empty bladders over nearly constant duration 21 ± 13 s. This feat possible, because larger animals have longer urethras thus, higher gravitational force flow speed. Smaller are challenged during by high viscous capillary forces limit urine single drops. Our findings reveal urethra a flow-enhancing device, enabling be scaled up factor 3,600 volume without compromising its function. study may help diagnose problems well inspire design scalable hydrodynamic systems based those nature.