I think the vascular disorder that is caused by smoking
is called peripheral vascular disease
, or PVT.
Smoking is a bad habit, and with luck this will convince lots of people not to start.
To answer your question, smoking puts chemicals in your bloodstream that act as "constrictors" that make your blood vessels tighten and clamp down. This is not normal, and is "reserved" for when you have "fight or flight" reactions from being scared, and when adrenalin rushes into your system.
When you fool your blood vessels into constricting over and over again for no reason (by injecting nicotiene and other strong stimulants), it creates issues with the tiniest of blood vessels and these are the ones that bring oxygen
and other nutrients all the way to your extremeties (fingers, toes, hands, feet).
When these are compromised for too long, they cannot repair themselves and go into a death spiral. Because there is no nutrient supply to the area, the body's natural repair mechanisms fail, and the problem gets worse, and again, the body has no tools (blood supply) to fix itself. Gangrene
is a circulatory problem. When the body parts cannot receive oxygen and nutrient-bearing blood, they die. Game over.
PVT is really caused by people stupidly believing that there is no real risk of smoking if they quit by the time they're 30 years old. Of course they're addicted by then, and 30 becomes 40, and then 50, and then, well, you know the rest.
Hope this helps scare you into quitting, or if you don't smoke, then I hope it scares your friends into quitting.