What is the Function of Veins in the Circulatory System?
Veins are vascular vessels that carry blood to the heart. They arise or are formed from venules which are small vessels carrying deoxygenated blood from the capillaries in tissues.
The pressure through veins is much lower than that of arteries and as a result of this veins have valves within them to prevent backflow of blood that may arise as a result of gravity. Because of the low pressure, you are unable to feel a pulse through a vein.
Almost all veins carry deoxygenated blood. An important exception to this rule is the pulmonary vein which carries oxygenated blood from the lungs to the left side of the heart so it can be pumped around the body.
Important veins to be aware of are the jugular veins which drain deoxygenated blood from the brain and the superior and inferior vena cava, which drain into the right atrium from the merging of veins from the top and bottom half of the body respectively.
Diseases that affect veins
Deep Vein Thrombosis (DVT)
A Deep Vein Thrombosis (DVT) is a blood clot that has arisen in a deep vein, commonly but not exclusively, in the leg. It can be caused by long periods of immobility (long haul flight or being in a plaster cast) or having a predisposition to clotting abnormalities of the blood.
The clot causes a blockage in blood flow resulting in pain and swelling. If left untreated part of this blood clot could break off, potentially blocking small vessels in the lungs creating a pulmonary embolism (PE). Any patient with a suspected blood clot should be urgently referred to the emergency services. Treatment of DVTs is with blood thinners that work to help the body break down the clot and clear the blockage.
Over time superficial veins in the leg succumb to the constant gravitational force they have to work against. They become dilated and increased backflow of blood occurs. They become more noticeable, and a relatively small impact can cause a bleed. A varicose vein bleed should be treated like any other bleed. Pressure should be applied with a bandage and the limb raised to limit blood flow into the bleeding limb.