Anatomy lab: wear scrubs. I usually wore scrub pants and a t-shirt. Sometimes I'd sport the scrub top.
I see no reason that they'd be unusable later. Just wash them regularly. Hell, I wore the same scrubs to the lab that I wore when I worked at the trauma center. If they can survive all the blood, pee, vomit, and God knows what else that they got on them when I was working there, they can survive a few fragments and goo from preserved dead bodies. You probably won't get THAT dirty in lab. At least not on a regular basis.
So my previous jobs: personal trainer and in the ER. My hobbies were/are sports and outdoorsy ****. So most of the clothing I own is conducive to those activities.
When its warm, I wear shorts, t-shirt, and usually a hat.
When its cold, I wear shorts, t-shirt, and usually a hat.
When its too cold for shorts, I wear scrub pants or sweat pants, because that's what I own. Sometimes I'll wear a hoodie or a fleece over my t-shirt.
Some people like to dress nice, but that's just their preference. If you see a lot of people dressed nice, its usually for the standardized patient practical, where they apparently want us to get pimped out. Typically, it is pretty casual, which is nice.
OMM and usually PCS lab is sports-type attire. T-shirt and shorts for guys, and the same for girls, but sports bra underneath. Sweat pants that you can pull up are usually acceptable. I once wore scrub pants to PCS on knee exam day, and Dr. Sampson made fun of me in front of everyone. I am now scarred for life.