The emissary veins are valveless venous vessels that connect the extracranial and intracranial venous systems. Note that the term emissary means “bridging” and in anatomy, it is used as an adjective rather than a proper name for every vein that establishes a connection between the dural venous sinuses and the veins external to the skull.
The function of the emissary veins is to provide selective cooling of the brain, as well as an alternative drainage route of the brain in the case of obstruction of dural venous sinuses. Furthermore, their clinical significance is reflected by the fact that they provide a pathway for the spreading of extracranial infections to the neurocranium.
|Definition||Veins that connect the extracranial with intracranial veins|
|Examples||Mastoid, parietal, supracondylar and occipital emissary veins, hypoglossal venous plexus, venous plexuses of foramen ovale, foramen lacerum and sphenoidal foramen, internal carotid venous plexus, petrosquamous sinus|
This article will discuss the anatomy and function of the emissary veins.
Anatomy and course
The emissary veins traverse various foramina of the skull, connecting the veins of the viscerocranium with those of the neurocranium. The number of emissary veins varies greatly among people. However, several emissary veins are defined as constant:
- The mastoid emissary vein, which passes through the mastoid foramen and connects the sigmoid sinus with the occipital or posterior auricular veins.
- The parietal emissary vein, which passes through the parietal foramen, connecting the veins of the scalp with the superior sagittal sinus.
- The hypoglossal emissary venous plexus, that traverses the hypoglossal canal and connects the internal jugular vein with the sigmoid sinus.
- The supracondylar emissary vein, that passes through the posterior condylar canal and connects the veins of the suboccipital triangle with the sigmoid sinus.
- The emissary venous plexus of foramen ovale, which connects the pterygoid plexus and the cavernous sinus.
- The emissary veins of foramen lacerum and the emissary vein of sphenoidal foramen (of Vesalius), that connect the cavernous sinus with the pharyngeal veins and pterygoid plexus.
- The internal carotid venous plexus that acts as an emissary plexus connecting the internal jugular vein with the cavernous sinus via the carotid canal.
- The petrosquamous sinus, as an emissary vein connecting the transverse sinus and retromandibular vein. Note that this sinus diminishes in the third trimester of pregnancy
- The occipital emissary vein, which connects the occipital vein with the confluence of sinuses via the occipital protuberance. Occasionally, it connects the occipital diploic vein with the occipital vein.
Explore our illustrations and quizzes to learn more about the blood vessels of the skull.