A varicose vein is an enlarged, twisted, engorged vein seen on the surface of the skin.  But, in order to understand what a varicose vein is and how it is formed, it is first important to understand the structure of a vein and how a vein works.  Here is a complete guide to the lifecycle of blood how how it can become pooled to created varicose veins.

How the Veins Work

Veins are part of the circulatory system, in addition to the arteries, heart, lungs, and of course blood, all which work together to supply oxygen to the body and dispose of carbon dioxide waste.  

The core components of the circulatory system:

How the Blood Moves through the Veins

Oxygenated blood is delivered to the body in the arteries. Arteries and veins are connected through a network, called capillaries. The capillaries are thin walled structures that allow for the oxygen to move into the body tissues and also pick up waste. After the blood enters the capillary bed from the arteries, it then moves into the veins, which deliver the carbon dioxide waste back to the heart for removal by the lungs.  

Although veins and arteries are both tubes that move blood through the body, they are structurally different.  

Arteries have Muscle & High Pressure to Move Blood

The lining of the artery has muscle within its walls, which can constrict and dilate, to facilitate the movement of blood.  In addition, the artery receives blood at a high pressure, as the heart must pump forcefully to move the blood into the arteries.  The pressure in the arteries reduces as it reaches the capillaries and then the veins have minimal pressure. 

Veins do not have Muscle to Move Blood

Unlike arteries, veins are floppy tubes that do not have any muscle to help move blood back to the heart. Instead, veins depend on the action of the body muscles to squeeze the blood back to the heart.  In order to keep the blood flowing against gravity to the heart, the veins have valves within them help to prevent blood from flowing backwards.

Faulty Veins Prevent Blood Flow back to Heart 

When the valves of the veins do not close properly or the vein is stretched preventing the valve from closing, blood is able to flow backwards.  This backwards flow of blood extends the walls of the vein, as they are not rigid structures, causing swelling of the vein.

Pooled Blood Creates Swollen Varicose Veins

This swelling allows more blood to accumulate in the vein and more difficulty moving the blood back to the heart.  The veins can swell so that they are visible on the skin. Even though varicose veins can be found anywhere in the body, it is usually found in the legs, as there is a longer distance for the blood to travel against gravity.