Where does all the gunk come from in a blackhead?

I've seen a lot of goop come out from them, and it looks like it's not physically possible, so can someone explain?Where does all the gunk come from in a blackhead?
blackheads and pimples are caused when a pore gets clogged with dirt, oil, and/or dead skin cells. If it gets infected it becomes a pimple which is why you see the white puss come out. The gunk from the blackhead is just the dirt and dead skin cells comming out.Where does all the gunk come from in a blackhead?
Blackheads are caused when dirt, oil, dead skin cells ect. get clogged up into your poors