Because my major (Construction Management) and my career path (Optometry) are quite different, there is hardly any crossover between the classes I take for my major and the prerequisites that I had to take to get into optometry school.
However, I can remember as specific time when there was crossover between my two college worlds:
It was between Construction Safety and Human Anatomy. I went to my Human Anatomy lab early one morning and learned about the circulatory system. We discussed and looked at all the veins and arteries in he body. My TA pointed out the femoral artery, which is huge. On the cadaver it was about as thick as my pinkie. He said that if that just punctured or pinched, you could die within an hour.
Later, I had Construction Safety, and we talked about fall harnesses. My professor explained that once you have fallen, the little loops around your legs pinch tightly and pinch your femoral artery closed. He said that you have about 30 minutes to rescue someone who has fallen from a roof or scaffolding before they completely blackout and then 10 more minutes until they die. To show is that this is true, we actually did a fall test. I thought they would do it on a dummy, but they asked for volunteers from the class. Rather than jumping off a roof (which can lead to some nasty leg breaks from the harness) we had a mechanical crane lift the guys up and hold then about 2 feet above the ground. Almost instantly their legs fell asleep and then started aching. By the end of it their legs were shaking and hurting, and they were only in the air for one minute. It was pretty crazy and it was pretty well ingrained in my mind that I really don't want to fall off of a roof.