Which bone does the spinal cord pass through its large opening?

The spinal cord passes through the large foramen magnum opening of the occipital bone. The foramen magnum is located in the back and bottom of the skull.

The occipital bone consists of four parts: the basilar part, two condylar parts and the squamous part. The basilar part sits in front of the foramen magnum and connects to the sphenoid bone. The squamous part is the curved piece behind it that cradles the brain, with the two condylar parts forming the sides. The foramen magnum also allows the accessory nerves, the vertebral arteries, the anterior and posterior spinal arteries, and the membrana tectoria and alar ligaments to exit through the occipital bone.