It is. They're what hold back
the URINE and feces.
The Big Bang Theory Season 8, Episode 18
It took me a gallon of URINE
to make that water.
The Big Bang Theory Season 5, Episode 15
that converts URINE
into drinking water.
The Big Bang Theory Season 5, Episode 15
...extracted from the URINE of cows.
The Big Bang Theory Season 4, Episode 22
...which could give
a positive URINE test for opiates...
The Big Bang Theory Season 1, Episode 5