The diploic veins (latin: venae diploicae) are large, valveless veins with a thin vascular wall in the diploe between the inner and outer layers of the cranial bones.
The diploic veins are connected with the cerebral sinuses by emissary veins.
The frontal diploic vein empties into supraorbital vein and the superior sagittal sinus, the anterior temporal into the sphenoparietal sinus and one of the deep temporal veins, the posterior temporal opens into the transverse sinus. The occipital diploic vein is the largest of all, that empties into the occipital vein or into either transverse sinus or the confluence of sinuses.