This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood Vessels of Abdomen and Pelvis, Subject name: Anatomy
True statement regarding portal venous system: 
Select and explain. 
A. Whole system is valve less, B. Valves are present at the junction of superior mesenteric artery and splenic artery, C. Valves are present in the intrahepatic system, D. There are about 10-12 valves along the entire course
A: Whole system is valve less
Answer: A: Whole system is valve less 
Explanation: Ans. (a) Whole system is valve lessRef BDC 4th ed. Vol. 11/268-71, Gray's 39th ed /1218-19* In adults, the portal vein and its tributaries have no valves.* In fetal life and for a short postnatal period valves are demonstrable in its tributaries, but they usually gets atrophied.* Rarely some persist in an atrophic form into adulthood.