Final answer:
The adult derivative of the wall of the myelencephalon is the medulla. The medulla oblongata is responsible for regulating vital functions.
Step-by-step explanation:
The adult derivative of the wall of the myelencephalon is the medulla. The myelencephalon corresponds to the medulla oblongata in adults.
The medulla oblongata is located at the base of the brain and is responsible for regulating vital functions such as breathing, heart rate, and blood pressure.