Sagittal section through the skull to show processes of duramater and venous sinuses
The sagittal section through the skull reveals the following dural folds and the dural venous sinus:
Dural folds: falx cerebri, falx cerebelli, and tentorium cerebelli. The diaphragma sellae is also present. However, it is not clearly visualized in the specimen.
Dural venous sinuses (colored blue): The major dural venous sinuses visualized in this specimen are the Superior and inferior sagittal sinuses, straight sinus and transverse sinus.
The dural folds are the folds of the meningeal duramater. The dural folds project into the cranial cavity and partially subdivide the cranial cavity. They include the falx cerebri, tentorium cerebelli, falx cerebelli, and the diaphragma sellae.
The falx cerebri is a crescent-shaped dural fold that projects downward between the two cerebral hemispheres from the dura covering the calvaria. It is attached anteriorly to the crista galli of the ethmoid bone and frontal crest of the frontal bone. Posteriorly it is attached to and blends with the tentorium cerebelli. The venous sinuses present in it are: superior and inferior sagittal sinus and straight sinus.
The falx cerebelli is a small midline projection of meningeal dura mater in the posterior cranial fossa. It is attached posteriorly to the internal occipital crest of the occipital bone and superiorly to the tentorium cerebelli. Its anterior edge is free and is between the two cerebellar hemispheres. The venous sinus related to it is the occipital sinus.
The tentorium cerebelli is a horizontal projection of the meningeal dura mater that covers and separates the cerebellum in the posterior cranial fossa from the posterior parts of the cerebral hemispheres. It is attached posteriorly to the occipital bone along the grooves for the transverse sinuses. Laterally, it is attached to the superior border of the petrous part of the temporal bone, ending anteriorly at the anterior and posterior clinoid processes.
The anterior and medial borders of the tentorium cerebelli are free, forming an oval opening in the midline (the tentorial notch), through which the midbrain passes. The venous sinuses related to it are: straight sinus, transverse sinus and superior petrosal sinus.
The diaphragm sella is a small horizontal shelf of meningeal dura mater that covers the hypophysial fossa in the sella turcica of the sphenoid bone. There is an opening in the center of the diaphragma sellae through which passes the infundibulum, connecting the pituitary gland with the base of the brain, and any accompanying blood vessels. The venous sinuses related to it are: anterior and posterior intercavernous sinus and cavernous sinus.
Dural venous sinuses :
The dural venous sinuses are spaces between the endosteal and meningeal layers of the duramater. They contain venous blood that are drained from the central nervous system, face and scalp. There are no valves in the sinuses or in the veins that are connected to the sinuses. The vast majority of the venous blood in the sinus drains from the cranium via the internal jugular vein
Superior sagittal sinus:
The superior sagittal sinus is an unpaired venous sinus along the attached margin of the falx cerebri. It allows blood to drain from the lateral aspects of anterior cerebral hemispheres to the confluence of sinuses.
Inferior sagittal sinuses:
The inferior sagittal is an unpaired venous sinus along the free margin of the falx cerebri. It drains to the straight sinus which connects to the transverse sinuses.
The straight sinus, also known as tentorial sinus is an unpaired venous sinus situated at the junction where the falx cerebri meets the tentorium cerebelli. The straight sinus receives blood from the superior cerebellar veins and inferior sagittal sinus and drains into the confluence of sinuses.
The transverse sinus (lateral sinus) is a paired venous sinus that runs through the tentorium cerebelli. It drains the venous blood from straight sinus on the left side and superior sagittal sinus on the right side. Both transverse sinuses begin at the internal occipital protuberance of occipital bone, while they terminate by giving off the ipsilateral sigmoid sinus. The sigmoid sinus then continues as the internal jugular vein.