*
The Bladder  

Copyright © Nucleus Medical Media, Inc.

The Female Urinary System  

Copyright © Nucleus Medical Media, Inc.

Urinary bladder function is a careful balance between pressure from the bladder to empty and resistance from the sphincter (valve) at its outlet. Pressure to empty increases suddenly when the bladder reaches a certain volume.

Sphincter resistance depends not only on the strength of the muscle but also on its position. Both forces are controlled mostly by your autonomic (automatic) nervous system, the same system that regulate