Deep-vein thrombosis: Blood clots in your veins

Let's play a quick game of free association. We say "blood vessel disorder," and you say the first thing that comes to your mind. Whether you are a healthy man or a patient, a primary care physician or a specialist, an epidemiologist or a lab researcher, your answer is likely to focus on the body's arteries. It's no surprise, since arterial diseases account for heart attacks (the coronary arteries), most strokes (the carotid arteries and smaller arteries in the brain), and many amputations (the leg arteries). And there's more: arterial disorders are also the culprits in many cases of kidney failure, dementia, intestinal bleeding, and even erectile dysfunction.

Healthy arteries are essential for good health. But the circulatory system has another set of blood vessels, the veins. Arteries carry oxygen-rich blood from the heart to all the body's tissues. Then veins swing into action, collecting the blood from the tissues and returning it to the heart and lungs so it can be circulated again and again.