It is sad to think that there animals farmed for the purpose of dissection. Not as sad for things like frogs, rats, chickens, etc., but I know cats and stuff have to be as well, too.
I did the normal dissections that everyone does (like the frog), but my senior year of highschool I took anatomy, and we dissected a variety of things; frogs, chicken wings, cow eyes, sheep hearts, rats (some of the rats my classmates dissected would be pregnant, so there would be tiny baby rats inside, sorta cool!), pig fetuses (that one was a little sad because it looked like a baby pig haha...).
It is kinda fascinating to see and learn about the insides of another creature.
I know vet academy students and up have to do the stuff like cats. No thanks. Never, would I ever. I just couldn't. (Well being a vet is sorta back up career idea for me so who knows, but it'd be awful either way)
But, think about it. Because those animals were dissected, veterinarians are able to learn how to help other animals. Because those animals were used to teach them, they can now help your pets if they get injured or sick. I think that makes up for everything, because animals are so precious, and there are humans who have been sorta dissected themselves (in the past when they were discovering how to treat wounds and ailments, they probably do now as well), and because of their generosity, doctors can also better help us.

It's important, otherwise we and our pets wouldn't have anyone to turn to if we were injured or sick!