大静脉

例句：

1. 1.The surgeon carefully removed the large vein from the patient's leg.
   外科医生小心地从病人的腿上取出了大静脉。
2. 2.Blood flow in the major veins helps to distribute oxygen throughout the body.
   主要静脉中的血流有助于将氧气输送到身体的各个部位。
3. 3.The doctor advised the patient to avoid standing for too long as it can strain the major veins.
   医生建议病人不要站得太久，因为这样可能会拉伤主要的静脉。