What is the unit of account of the bitcoin system?

As a keen observer of the cryptocurrency landscape, I'm curious to delve deeper into the intricacies of the bitcoin system. Could you elaborate on what the unit of account within this system actually is? I understand that bitcoin functions as a digital currency, but I'm interested in knowing the specific denomination or unit that serves as the fundamental measurement for transactions and valuations. This knowledge would help me better grasp the economic dynamics and monetary policy implications of the bitcoin ecosystem.