In this note, we will consider the anatomy, areas of venous drainage, and anastomoses of the emissary and diploic vein.
The venous system of the head has a complex structure. The veins form a large number of anastomoses among themselves, which provide a fairly intensive drainage of venous blood from the head region.
These anastomotic, that is, communicating vessels include diploic and emissary veins.
Diploic veins (vv. diploicae).
They drain venous blood from the bones of the cranium and at the same time communicate the dural venous sinuses, the emissary veins and the superficial veins of the head between each other.
They are located in the canals of the spongy bone of the cranium called diploic canals (canales diploici), and they closely adhere to their surfaces and therefore do not collapse. There are no valves in their walls. The peculiarity of these veins is the presence of special cells filled with lymphoid tissue in their outer sheath.
Let’s consider the largest diploic veins.
The occipital diploic vein (v. diploica occipitalis) is the largest in this group of veins. It passes through the thickness of the occipital bone. It communicates the transverse sinus with the occipital vein.
The frontal diploic vein (v. diploica frontalis) is located in the spongy bone of the squamous part of the frontal bone. It communicates the superior sagittal sinus with the supra-orbital vein.
The anterior temporal diploic vein (v. diploica temporalis anterior) passes in the thickness of the lateral area of the squamous part of the frontal bone. It communicates the deep temporal vein with the sphenoparietal sinus.
The posterior temporal diploic vein (v. diploica temporalis posterior) lies in the thickness of the temporal and parietal bones. It communicates the occipital vein with the transverse sinus.
In addition to anastomoses with other venous systems, diploic veins can anastomose with each other.
Emissary veins (vv. emissariae) – are also called draining veins. They are short anastomoses between the dural venous sinuses and the superficial veins of the head. They pass through the open-ended canals of the bones of the cranium. It should be noted that in the lumen of these veins, the blood flow may have the opposite direction. It depends on fluctuations in intracranial pressure.
Let’s consider the largest emissary veins.
The parietal emissary vein (v. emissaria parietalis) passes through the foramen of the posterior part of the parietal bone
It communicates the superior sagittal sinus and the superficial temporal vein, as well as the posterior temporal diploic vein with the superficial temporal vein.
The mastoid emissary vein (v. emissaria mastoidea) is located in the mastoid canal of the of the temporal bone.
It communicates the sigmoid sinus with the occipital vein.
The condylar emissary vein (v. emissaria condylaris) passes through the condylar canal of the occipital bone. It communicates the sigmoid sinus with the atlanto-occipital sinus. It also forms an anastomosis between the deep cervical veins and the vertebral venous plexuses.
The occipital emissary vein (v. emissaria occipitalis) passes in the bony canal under the external occipital protuberance. It communicates the confluence of sinuses with the occipital vein. The occipital emissary vein is irregular, an may be absent in healthy people.
There are a number of venous plexuses, which can also be attributed to emissary veins:
The venous plexus of the foramen ovale (plexus venosus foraminis ovalis) passes through the foramen ovale of the sphenoid bone. It also communicates the cavernous sinus with the pterygoid plexus.
The venous plexus of the sublingual canal (plexus venosus canalis hypoglossi) passes in the canal of the same name of the occipital bone, where the sublingual nerve is also located. This plexus communicates the internal jugular vein with the anterior vertebral venous plexus.
The internal carotid venous plexus (plexus venosus caroticus internus) is located in the carotid canal along with the internal carotid artery. It communicates the cavernous sinus (sinus cavernosus)
with the pterygoid venous plexus (plexus pterygoideus).
Emissary and diploic veins of the cranium
- Diploic veins
- vv. diploicae
- Diploic canals
- canales diploici
- Occipital diploic vein
- v. diploica occipitalis
- Frontal diploic vein
- v. diploica frontalis
- Anterior temporal diploic vein
- v. diploica temporalis anterior
- Posterior temporal diploic vein
- v. diploica temporalis posterior
- Emissary veins
- vv. emissarii
- Parietal emissary vein
- v. emissaria parietalis
- Mastoid emissary vein
- v. emissaria mastoidea
- Emissary veins
- vv. emissariae
- Condylar emissary vein
- v. emissaria condylaris
- Occipital emissary vein
- v. emissaria occipitalis