Veins carry blood back to the heart. The deep veins within the muscles are the main pathway for blood return. Superficial veins just under the skin help with blood return, but are may be removed or closed and blood will find another way to return to the heart. The superficial and deep system are connected by perforating veins.
When we walk, the calf muscles compress the deep veins in the calf pumping the blood back to the heart. When the muscles relax, gravity pulls the blood back towards the feet. There are one-way valves in the veins that close when the blood attempts to move backwards, allowing only flow towards the heart. Primary vein disease is caused by genetic variation in the strength of the vein wall and valves, where the valves may fail leading to vein disease.
Vein disease may manifest in leg symptoms that may affect one’s ability to enjoy life and complete necessary activities. The disease and its severity progresses with time.