Which of the following is an anatomic feature unique to vein
     Which of the following is an anatomic feature unique to veins?  smooth muscle in the tunica media  valves to prevent backflow of blood  in the tunica external  tunica media consists only of endothelium and a basement membrane 
  
  Solution
Answer: b. valves to prevent backflow of blood
Explanation- The pressure of the blood is low in veins and valves maintain unidirectional flow of blood. Veins carry deoxygenated blood from the peripheral tissue to the heart.

