The cell that's producing the signal produces enough of the molecule so that it enters the bloodstream, it circulates throughout your body, eventually it reaches a cell at a great distance, which has a receptor for that ligand and the signal gets received.

发出信号的细胞产生信号分子,数量十分充足 能够进入到血液中,信号随着血液流遍全身,最终到达较远处的细胞,在这些细胞上有与配体配对的受体,信号被细胞接收

耶鲁公开课 - 生物医学工程探索课程节选

Here, what's different between autocrine and paracrine is that there's some distance between the cell that produces the signal and the cell that receives the signal, but it's not too great a distance because the blood system doesn't have to be involved.

自分泌和旁分泌的区别在于,旁分泌中,产生信号的细胞和接收信号的细胞,之间存在着一定的距离,但这个距离并不远,因为血液系统并不参与

耶鲁公开课 - 生物医学工程探索课程节选