I am using MacBook Pro 13 .current OS X El Capitan
Full macOS 10.xx updates (i.e. the Update that gets a new name) can be retrieved from the AppStore, yet instead of looking for it in Updates you need to search for them.
Usually however, you only get the newest compatible OS shown in AppStore so you'd need to visit Apples website to retrieve e.g. HighSierra.
As @davidanderson has pointed out you can find a more detailed list of Apples OS updates and installers here on AD.