How do the Switch's Joy-Con shoulder buttons work when in horizontal mode?

This is something I've been trying to figure out since the reveal trailer. Just what goes on with the shoulder buttons on the Switch's Joy-Cons? Are there more shoulder buttons revealed when the Joy-Cons are slid out? Do the existing shoulder buttons still function? That would seem quite awkward if you were using the left-hand Joy-Con, but not so bad for the right hand.

I also looked at the best images I could to see if there were extra shoulder buttons revealed on the Joy-Cons once they are detached from the screen. I can't make that out for sure. I've provided the images above. Let me know what you think!