Hello everyone! This is Matt from Kenhub, and in this tutorial, we are going to look at the petrosal sinuses which are dural venous sinuses.
Before we look at the petrosal sinuses, let's first define what we mean when we talk about the dural venous sinuses. They are basically intracranial venous channels that drain venous blood from the brain and the meninges to the internal jugular veins. They are situated between the endosteal and meningeal layer of the dura mater and their walls are lined with an endothelial lining. These venous channels are also valveless; in other words, unlike most veins, the dural venous sinuses do not contain valves which allows for bidirectional blood flow within these vessels. So now you have a brief description as to what the dural venous sinuses are, let's get back to looking at the petrosal sinuses.
The petrosal sinuses are paired dural venous sinuses. There are four petrosal sinuses leaving the middle cranial fossa. Two superior petrosal sinuses – one of the left side and one on the right side – and two inferior petrosal sinuses – also located bilaterally.
The superior petrosal sinus runs along the superior aspect of the petrous part of the temporal bone in the base of tentorium cerebelli in the groove called the groove for the superior petrosal sinus. It crosses over the trigeminal nerve before it enters Meckel's cave and it terminates in the proximal part of the sigmoid sinus.
The superior petrosal sinus receives venous blood from the cerebellar veins which drain the cerebellum. The inferior cerebral veins which drain the inferior surface of the cerebral hemispheres particularly the inferior cerebral veins that drain the undersurface of the temporal lobe. And, finally, the superior petrosal sinus receives venous blood from the labyrinthine vein which drains the structures of the inner ear. It drains into the sigmoid sinus.
The inferior petrosal sinus runs in a shallow groove called the inferior petrosal sulcus between the petrous part of the temporal bone and the basilar part of the occipital bone. It travels from the posterior aspect of the cavernous sinus towards the distal part of the sigmoid sinus inferior to the fibers of the seventh cranial nerve – the facial nerve – and the eighth cranial nerve – the vestibulocochlear nerve.
The inferior petrosal sinus receives venous blood from the cavernous sinus and the labyrinthine veins as well as some tributaries from the medulla oblongata, pons and the inferior surface of the cerebellum. It passes through the jugular foramen and joins with the sigmoid sinus to form the internal jugular vein into which it drains.
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