portal circulation

例句：

1. 1. The portal circulation is a crucial part of the immune system.
   门户循环是免疫系统中至关重要的一部分。
2. 2. In this study, we focused on the portal circulation of drugs in the human body.
   在本研究中，我们关注了药物在人体中的门户循环。
3. 3.The researchers found that the portal circulation of nutrients was significantly reduced during the pandemic.
   研究人员发现，疫情期间营养物质的门户循环显著减少。