What portion of the brainstem blends with the spinal cord after passing through the foramen magnum?

The medulla oblongata is the portion of the brainstem that blends with the spinal cord after passing through the foramen magnum.

The medulla oblongata is the lowest part of the brainstem and is continuous with the spinal cord after passing through the foramen magnum. The medulla oblongata is cone shaped and it contains several nerve cells which controls many autonomic (involuntary) functions such as breathing, sneezing, heart and blood vessel activity, swallowing and digestion. The medulla oblongata is the center for respiration and circulation and it also assist in transmitting messages between various parts of the brain and the spinal cord.