At the boundary between the papillary layer and reticular layer, the collagen fiber has a small quantity and its weave is loose, which weakens the connection of this two layers, if treated improperly, the skin would tend to separate into two layers. 在乳头层和网状层的分界处,胶原纤维稀少并且编织疏松,使得两层之间的连接较弱,如果处理不当会导致两层分离。