Well, the endocrine system is a body organ system that is specialized in producing these kinds of signals that are used - that accumulate in the blood and are used by cells all over the body.

内分泌系统是一种,作用于周身各器官的系统,它专门产生这些有用的信号,这些信号在血液中聚集,全身各处的细胞都可利用

耶鲁公开课 - 生物医学工程探索课程节选