You likely know that the central nervous system is surrounded by a connective tissue sheath called mater. There are three layers: the pia mater, the arachnoid mater and the dura mater. These three layers surround both the brain and spinal cord, lining the skull and spinal canal. Many connective tissue sheaths in the body invaginate deeper into the tissue and the same is true of the brain. The pia mater is like the skin of the brain. Whereas the sheets of connective tissue that we’re considering in this post are extensions of the dura mater which also lines the skull.
In the image above, you can see both a horizontal structure and a vertical structure. The horizontal structure is the tentorium cerebelli. It divides the cerebrum above from the cerebellum below. One could experience it as the ceiling of the cerebellum or the floor for the occiptal lobes. It attaches to the petrous part of the temporal bone (behind the inner ear) and travels backward to the occipital bone where it encases the transverse sinuses.
The vertical structure is the falx cerebri. It divides the right and left hemispheres of both the cerebrum above and the cerebellum below. The falx cerebri attaches to the crista gali of the ethmoid bone anteriorly. It follows the midline of the body superiorly containing the sagittal sinus. It extends as far back as the internal occipital protuberance.
The two structures are continuous with one another as you can see below.
Close your eyes and begin to imagine these structures in you head. Look at different pictures to help you orient these structures in relation to your ears, sinuses, eyes, palate. Begin to include the falx cerebri in the image you have of your midline structures. Practice aligning it with the center of your throat and breastbone. Begin to imagine this horizontal structure – the tentorium cerebelli – at about the level of your ears. Let it help you find right-left balance in the head.