Tagged: gravity

Universal urination duration in mammals

Nature is a source of all kinds of inspirations, some more original than others. This one I found very exceptional and so I thought: “Lets share it on our blog!”
At Georgia Tech (George Woodruff School of Mechanical Engineering and School of Biology) they have been studying how fast animals urinate…yes, how they pee. They found out that all animals weighing more than 6.6 pounds (3 kg) urinate in 20 seconds, on average. So an elephant (18 L bladder capacity) urinates in the same amount of time as a cat (5 mL bladder capacity). It all has to do with the length of their urethra: Larger animals have longer urethra, which increases flow rate because of higher pressure. An elephant urinates the same volume per second as five showerheads. Can you imagine standing under a peeing elephant?

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This study disproves a previous hypothesis that urinary flow is controlled by bladder pressure generated by muscular contraction; and instead suggests urination is powered by the force of gravity rather than external pressure.
They demonstrated the feasibility of this by showing that a teacup, quart and a gallon of water emptied at a same rate, using varying lengths of connecting tubes. This is an interesting insight that could inform liquid dispensing systems, as it’s not the capacity of the tank that determines the dispensing rate, but it’s the connector tube. Any ideas?

Cool, right? I just have one remark. I think humans are an exception – I still hold the record of longest urinator with my 1 minute 43 seconds… but maybe it’s just me who can’t do it in 20 seconds.

Link: http://www.news.gatech.edu/2014/06/30/study-animal-urination-could-lead-better-engineered-products
Journal reference, published in PNAS: Duration of urination does not change with body size – Patricia J. Yanga, Jonathan Phama, Jerome Chooa, and David L. Hu

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