What structure extends into the longitudinal fissure between the cerebral hemispheres?

The falx cerebri is a sickle-shaped structure made of dura mater that extends into the longitudinal fissure, which separates the left and right cerebral hemispheres. Its primary function is to provide support and stabilization for the brain, preventing excessive movement between the two hemispheres. The falx cerebri attaches to the crista galli at the front and extends back to the tentorium cerebelli, anchoring itself to the skull while creating a partition between the hemispheres. This anatomical feature plays an essential role in protecting the brain and maintaining its structural integrity.