Which of the following statement regarding poal venous system is TRUE?

In adults, the poal vein and its tributaries have no valves. In fetal life and for a sho postnatal period valves are demonstrable in its tributaries, but they usually atrophy. Rarely some persist in an atrophic form into adulthood. Poal venous system comprises of poal vein and its 3 tributaries, splenic vein, superior and inferior mesenteric vein. Thses veins drain the blood from the intestinal tract, from the oesophagus to the rectum, from the spleen and pancreas to the liver. Poal vein carries 75% of total blood flow to the liver. Normal poal pressure is 5 - 10mmHg.