Final answer:
The filum terminale is the structure that anchors the spinal cord inferiorly. It is an extension of the pia mater and connects the spinal cord to the coccyx.
Step-by-step explanation:
The structure that serves to anchor the spinal cord inferiorly is known as the filum terminale. The filum terminale is an extension of the pia mater, one of the protective coverings of the spinal cord, which extends downward from the apex of the conus medullaris (the tapered end of the spinal cord) and blends with the dura mater to anchor the spinal cord to the coccyx.