The Project Manager is a human ESB, a Human Service Bus (HSB).

The HSB receives messages from humans, transforms them, aggregates them, sometime filters them, and forwards them to other humans or HSBs.

And they do that, following the corporate processes.

Like an ESB the HSB is a nodal point in an enterprise organization and, like an ESB, they can be a source of massive system failures.

Image Credits: Nickster 2000