So how does the urethra close?

Body: 

This question is about incontinence. When we cough or sneeze how does the urethra keep us continent? Is it because the external sphincter increases closer automatically (due to intraabdominal pressure), or is it because the pressure from above squashes it closed?
(sorry I was reading about this in one of Christine's replies and now I'm confused)
Thanks & kind wishes to all xxx

Hold that thought! I'll address it in my blog with illustrations and diagrams. It's so complex even medical science admits they do not understand it completely. However, there are some basic concepts that play major roles we can discuss. It will be Thursday before I can post it.

Thanks so much. I am curious to know how it works. xxx