This is a very nice dungeon with an inherent logic, why everything is there (which I always like). I really appreciate the little backstory the players could discover - whatever happened to Mariel? They are not accounted for? - possibly turning this into a rescue mission.
What I miss is as reason for the group to go in there, but that might be my “Please hold my hand”-5e-brain there :)
Littlelest nitpick: It is the heart pumping blood, not the blood vessels.