Valveless veins

The valveless veins are veins that lack venous valves. Most veins contain valves (known as the valvula venosa in the TA) to prevent backflow, i.e. ensuring that blood flow is always towards the heart .

Recent evidence shows that veins that were previously thought to be valveless, are now known to have valves, including the facial and superior ophthalmic veins .

Valveless veins are common in the central nervous system .

List of valveless veins

• brachiocephalic veins
• dural venous sinuses
• portal venous system
• superior vena cava (SVC)
• Thebesian veins
• vertebral venous plexuses