Here is a color-coded diagram of how the printhead is built. The only difference is that there 3 ink nozzles in a row instead of over 40.

Ink flows from the cartridge into the printhead through the red circles.

Ink flows into chambers underneath the piezo elements (marked by orange lines).

Individually addressable piezo elements for each nozzle cover the ink chambers.

The piezo elements are connected to a common ground by metal strips.

(Second image) The ribbon cable (shown as a blue overlay) connects the other terminal of all the piezo elements to the multiplexer.