This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
Umbilical vein becomes --- in adults: 
Select and explain. 
A. Ligamentum teres, B. Ligamentum venosum, C. Medial umbilical ligament, D. Ligamentum aeriosum
A: Ligamentum teres
Answer: A: Ligamentum teres 
Explanation: In adult liver, left umbilical vein becomes ligamentum teres, it runs in the falciform ligament into the umbilical fissure. Initially, the umbilical veins drain into the sinus venosus but at 5 weeks of development they begin to drain into the hepatic sinusoids. The right umbilical vein ultimately disappears and the left umbilical vein later drains directly into the hepatocardiac channel bypassing the hepatic sinusoids through the ductus venosus. Remnant of ductus venosus becomes the ligamentum venosum at the termination of the lesser omentum under the left liver.