Fig. 5: Urothelium expansion and contraction in response to bladder filling and emptying.
From: The urothelium: a multi-faceted barrier against a harsh environment
a Umbrella cells in its relaxed/unfilled state, (b) the bladder filling stimulates exocytosis of the vesicles coupled with endocytosis, (c) the exocytosis of the vesicles leads to increase in umbrella cell apical membrane. The endocytosed vesicles are delivered to lysosomes where the contents are degraded, (d) upon voiding, the added apical membrane is internalized, and a new pool of vesicles are formed in the Golgi.
