What structure passes through the foramen magnum?

The structure that passes through the foramen magnum is the spinal column, specifically the spinal cord, which is an extension of the central nervous system. The foramen magnum is a large opening at the base of the skull that allows for the passage of the spinal cord as it connects to the brainstem. This connection is crucial for the transmission of nerve signals between the brain and the body, facilitating various bodily functions and reflexes.

In contrast to this, the other structures mentioned do not pass through the foramen magnum: the head's muscles are primarily located and attached to the skull and do not pass through this specific opening; the optic nerve is responsible for vision and originates from the eyes, traveling towards the brain but does not go through the foramen magnum; and while the carotid artery supplies blood to the brain, it enters the skull through different openings, primarily the carotid canal, rather than the foramen magnum. Thus, the spinal column is the correct choice as it is directly involved in the pathway that allows the central nervous system to connect with the rest of the body.