Generally, you can use the command "gnome-open" for this kind of stuff. Applied to either a file or a directory, it would open them with the applications associated to them.
(full path to be sure) would open the directory "Pictures" in Nautilus.
would open the image "Photo.jpg" in the currently set default application, in my case Eye of Gnome (Image Viewer).
And so on.
However, you can, of course, also run the respective application directly and pass the file/directory to it, like this:
Whatever is easier or fits better in a specific case.