If you stab somebody in the bladder will their pee spill out?

no, it would just bleed. unless you have a really long "thing to stab with" then there's a 26% chance of urine mixing in with the black expossed blood cells.

between the two muscle layers is the myenteric or auerbach's plexus, which controls peristalsis. in the colon, the muscularis externa is much thicker because the feces are large and heavy, requiring more force to push along. the stomach has a third layer of muscularis externa: the inner oblique layer.