What are these tubes on skull of woodpecker?

I’m busy with skinning my first (green) woodpecker. I’m located in the Netherlands and bird is registered at the proper authorities. I have skinned dozens of small birds, like canaries, parakeets, agapornis etc. But.. I have never seen these tubes on these small birds running from the top of the skull to the tongue. It is quite sticky as well.

Who knows what these are and are the specific for woodpeckers?