Apical bulkhead structure persists at high luminal pressure. (a) Schematic representation of the microinjection setup used to acutely raise intraluminal pressure in the BC. Blue arrows indicate direction of flow. Created with BioRender.com. (b) Still images from live-cell time-lapse brightfield microscopy before and during microinjection of fluid into a BC (see also Video 2). White arrowhead indicates the position of an apical bulkhead. Scale bar: 10 µm. (c) Quantification of the fold increase in BC diameter before microinjection of fluid into BC causes blebbing of the apical membrane into the cytoplasm (n = 9, obtained in three independent experiments).