The internal occipital crest is a bony ridge that runs vertically along the internal surface of the occipital bone in the back of the skull. It extends from the foramen magnum, which is the large opening at the base of the skull through which the spinal cord passes, to the internal occipital protuberance. The internal occipital crest serves as an attachment site for muscles, ligaments, and membranes that support the brain and spinal cord. It also helps to provide structural stability to the skull.