Why when people are stabbed in the foot they bleed from their mouth ?

i've seen this happen in both kill bill volume one to gogo yubari and then in gladiator in noe of the battles.

i've always wondered why this happens and how?Why when people are stabbed in the foot they bleed from their mouth ?
is that what really happens???? do a test take a knife stab it in your foot and see if that happens. :)Why when people are stabbed in the foot they bleed from their mouth ?
did you get that from movies....hollywood takes everything to the next level...they exaggerate everythingWhy when people are stabbed in the foot they bleed from their mouth ?
It probably just made them bite their tongue or something.