I'm just a dentist, but we do see the effects of ruptured vessels during frequent oral surgeries performed in our office.
A ruptured vessel can be an insidious thing. We've seen people with extracted wisdom teeth that left with little of no bleeding suddenly bleed out two to four hours later. Once the patient even had to go to the emergency room. A slightly nicked vessel perhaps? But could kill them just the same.
Trying to extrapolate from my dental experiences, but I could see two different scenarios.
1. A small vessel ruptured by the impact, slowly bleeds until the lungs are filled and death occurs.
2. A small vessel is damaged, but doesn't rupture immediately, then begins to bleed later. Arteries are likely to be more of a concern than veins. More pressure means a more rapid bleed. I've seen patients mouths fill to the top and then overflow in less than twenty seconds.
Pure speculation obviously, but I strongly feel that the lack of a fractured bone would not preclude a traumatic bleed out.
