The diploic veins are large, thin-walled valveless veins that channel in the diploë between the inner and outer layers of the cortical bone in the skull, first identified in dogs by the anatomist Guillaume Dupuytren.

[1] A single layer of endothelium lines these veins supported by elastic tissue.

The diploic veins drain this area into the dural venous sinuses.

[1] The frontal, which opens into the supraorbital vein and the superior sagittal sinus.

It has been noted that "The tunnels formed by diploic veins are among the few known skeletal markers of soft tissue alteration".