Falx cerebri

Anatomy

The brain and spinal cord are enveloped by the meninges, which serve to protect them from mechanical trauma, provide support to blood vessels and a passageway for the cerebrospinal fluid (CSF). From innermost to outermost, the meninges consist of the following three layers: pia mater, arachnoid mater, and dura mater.

The dura mater is a strong, double-layered membrane, composed of the periosteal layer, which adheres to the periosteum of the neurocranium, and the meningeal layer, which surrounds the brain and spinal cord. In some regions and fissures of the brain, the meningeal layer of dura mater projects inwards to form four dural partitions: the falx cerebri, falx cerebelli, tentorium cerebelli, and sellar diaphragm.

The falx cerebri is the largest of the four partitions of the dura mater, and represents an invagination of the meningeal layer of dura into the longitudinal fissure of the brain. This crescent-shaped sheet of tissue occupies this fissure and separates the two cerebral hemispheres. It begins anteriorly from the crista galli of the ethmoid bone, and runs in the midline along the entire internal surface of the cranium, and extends posteriorly all the way to the internal occipital protuberance.

The anterior part of the falx cerebri is narrow and thin, and is fixed to the crista galli. Its convex superior margin is attached to the lips of the groove for superior sagittal sinus, while its concave inferior margin is free. The posterior part of the falx cerebri is broad and attaches to the internal occipital protuberance, while blending with the superior surface of the tentorium cerebelli.

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Relations

The falx cerebri contributes to the formation of several dural venous sinuses:

• The convex superior margin of the falx cerebri houses the superior sagittal sinus, which runs along the midline of the internal surface of the calvaria, in the groove for superior sagittal sinus.
• The concave inferior margin of the falx cerebri runs in the interhemispheric space and contains the inferior sagittal sinus.
• The posterior part of the falx cerebri contains the straight sinus, more specifically along the line of attachment of the falx cerebri and tentorium cerebelli.

Function

The falx cerebri separates the cerebral hemispheres and houses the dural sinuses, into which the blood and cerebrospinal fluid drain. However, it’s exact function is not entirely certain. The function of the falx cerebri may be to constrain the brain and limit its displacement and rotation inside the cranium. Being a dural fold, the falx is stiffer than the surrounding tissue and plays an essential role in supporting the brain by suppressing the movements of the brain inside the skull during acceleration.

In addition, it is thought that the dural folds, and especially the falx cerebri and the tentorium cerebelli, play an important role in the development and functional loading of the cranium. In other words, dural folds determine the cranial suture sites and their absence is accompanied by a lack of suture formation.

Now that you’ve mastered the falx cerebri, check out the study unit below to find out more about the meninges of the brain, or take the quiz to consolidate what you learned so far!