Confluence of sinuses
The confluence of sinuses (torcular of Herophilus or torcula) is a dural venous sinus that appears as a dilation at the posterior end of the superior sagittal sinus. It is located on the caudal aspect of the brain, around the internal occipital protuberance of the occipital bone.
Functionally, this vessel represents a junction between the superior sagittal, straight, occipital and the two transverse sinuses; it facilitates the blood drainage from the superior sagittal, straight and occipital sinuses to the bilateral transverse sinuses that carry the blood towards the internal jugular vein.
|Superior sagittal sinus, straight sinus and occipital sinus
This article will discuss the anatomy and function of the confluence of sinuses.
Like the other dural venous sinuses, the confluence of sinuses has no valves and contains no muscle tissue in its walls. Its endothelial-lined walls are instead made up of the periosteal and meningeal layers of dura mater, which is the outermost layer of the meninges of the brain.
Typically, pressure and gravity will drive blood from the superior sagittal, straight, and occipital sinuses, into the confluence of sinuses, then laterally into the transverse sinus, destined for the internal jugular vein via the sigmoid sinus. However, since the dural venous sinuses are valveless, blood is allowed to flow in either direction.
To learn more about the dural sinuses of the brain, check out our articles, quizzes, and videos.
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