internal vein

例句：

1. 1. The doctor found a small internal vein that was causing the swelling.
   医生发现一个小的内静脉引起了肿胀。
2. 2. The surgeon removed the internal vein to relieve the patient's pain.
   外科医生切除了内静脉以缓解病人的疼痛。
3. 3. The researcher discovered an unusual internal vein in the sample tissue.
   研究者在样本组织中发现了不寻常的内静脉。