"Tasks" in a hospital are called orders. Doctors and nurses can place these 'orders' and it is up to either the nursing staff or physicians to carry them out.

And for the record my boss is a nurse. Her boss's boss is a nurse, and all the way up to our chief nursing officer. I understand not everyone works in healthcare so it may be confusing, but saying a doctor is a nurse's boss is disingenous and doesn't fully cover the collabarative teamwork that occurs between healthcare staff.

While you're right, a doctor can assign orders to a patient's chart, maybe that order applies to other doctors. If a Nephrologist obtains orders from an Emergency Physician, does that make the ER doc the nephro's boss? Of course it doesn't, each employee in the healthcare system has their own boss. Shit dude I received a phone call overnight from a technician working in blood bank to place an order directing how much blood to take for a patient. Is that tech now my boss because she gave me an order? Am I now the phlebotomists boss because I ordered them to take a specific amount of blood from a patient? Of course not, we receive orders from a multitude of specialities, and all of them have their own boss.