Representative pictures of CD31 immunohistochemistry-PAS double staining and contrastive analysis between EV and VM. a EV was positive for CD31 and PAS, whereas VM was negative for CD31 but positive for PAS. EV was labelled by black box and VM was marked by red box. b EV density was obviously more than VM density per 200× field. Data were represented as mean ± S.D. n = 40. c The connection between EV and VM was distinctly observed under CD31-PAS double staining (400×). EV was labelled by black box and VM was marked by red box. d Schematic drawing of VM and EV in two dimensional plane. When blood flows through smaller EV and bigger VM, there may be a switch between laminar flow and turbulent flow. e Comparison of vascular diameter between EV and VM under CD31-PAS double staining (400×). f The vascular diameter of VM was four times bigger than that of EV. Data were represented as mean ± S.D.