Here's the close up of the brew path.
The water entry should be obvious, then it travels up, thru the bright green section, thru the filter screen (transparent grey), down thru the gicleur (yellow), into the valve section (blue). The valve is shown closed.
When the orange cam rotates up (it's attached to the lever), it pushes up the valve seal (yellow) and brew water floods the cam area, then goes up towards the infamous allen screw. (Now it should be apparent why it's there as well. It would be hard to drill around that corner.)
Then down toward the dispersion disk.
Please pardon the jpg. I resized it and added the text with free software and it mangled some areas (particularly the reds), but you get what you pay for.
Also pardon my part names. Not sure I'm using the proper names, what I'm talking about should be clear though (I hope).
Anyway, does that make sense? Are any parts of the picture unclear?