Blood vessels that carry blood towards the heart are called veins. Except for the pulmonary and umbilical veins, most veins carry ‘impure’ or deoxygenated blood to the heart. Most of the veins have valves which prevent backflow of blood (regurgitation).
Phlebology is study of veins and their diseases. A specialist in phlebology is known as phlebologist.
Superficial veins are close to the surface of skin and deep veins lie deeper within the muscles. These two types are connected through perforator veins with blood flowing unidirectional from superficial veins to deep veins.
Veins return oxygen-poor (deoxygenated) blood from organs to the heart. Capillaries, the smallest of the blood vessels embedded within tissues of organs, join together to form post-capillary venules. The post-capillary venules join together to form larger venules which in turn converge to form larger veins. These veins finally join the largest veins in the human body – the superior vena cava and inferior vena cava, which carry the blood to the right upper chamber (atrium) of the heart from the upper half and lower half of the body respectively. Most of the veins of the heart (cardiac veins) drain into the coronary sinus which empties into the right atrium. The valveless, smallest cardiac veins known as thebesian veins drain the heart muscle and empty directly into the heart chambers.
The deoxygenated blood is pumped from the right atrium à right ventricle à pulmonary artery à lungs. The pulmonary veins carry oxygen-rich (oxygenated) blood from the lungs to the left atrium of the heart.
Diseases affecting the veins:
a. In venous insufficiency there is inability of veins to pump enough blood back to the heartdue to weakened walls and damaged valves. It is usually exhibited as spider veins (dilated veins) or varicose veins (enlarged and twisted veins). It is treated with compression, vein stripping, thermal ablation, phlebectomy, sclerotherapy, etc.
b. Blood clot formed in a deep vein can cause deep vein thrombosis (DVT). The clot can detach (embolization) and travel to the lungs leading to pulmonary embolism, a potentially life-threatening condition. It is treated with anticoagulant drugs.
c. Thrombophlebitis is inflammation of the veins due to blood clots. Treatment options are medications, surgical removal, stripping or vein bypass.
d. Postphlebitic syndrome is venous insufficiency caused due to DVT, abnormal connection between artery and vein, obesity, etc. Compression stockings, medication, ligation, vein stripping, surgery, etc. are the treatment options.