Every curriculum is different and depends on if you are traditional lecture, PBL, etc, so there will occasionally be group work such as in anatomy lab, PBL groups, and so on that you will develop friends and groups. You can also find people to study with and let it develop that way as well. I wouldn't worry about that too much, especially if you're already putting the thought in the forefront of your thinking. Many schools also have social events as mentioned above, not to mention club meetings and club events (be it for the specific club or that the club is hosting it for everyone).