Question

What is incorrect about a vein?

• A. A vein has a thinner wall compared to an artery
• B. Blood flows at zero pressure through a vein
• C. Blood tends to flow backwards through a vein
• D. There are valves in a vein

Answer 1

The correct option is B Blood flows at zero pressure through a vein

Blood flows at a lower pressure than an artery through a vein, but the pressure is not zero. It has an average value of 80 mm Hg. However, since the pressure is lower than that in an artery, blood sometimes tends to flow backwards in a vein. To prevent this backward flow, a vein has valves. A vein has a thinner wall than an artery because of the lower pressure of blood in it.