And at the portions where they overlap, these overlapping portions act as one way doors. And when there is a fluid build up inside the tissue, that fluid pressure pushes on these overlapping sections, these one way doors. And that opens these endothelial cells and allows fluid to actually flow into the endothelial cell. So for example, let's imagine that we have a build up of pressure here. And so the fluid pushes against the overlapping portion and the fluid moves into this cavity, this region of our lymph vessel. Now, as the fluid builds up in the lymph vessel, it pushes back onto this side, the other side of our endothelial cell.