Excitability and contractility in arterioles and venules from the urinary bladder

The urinary bladder performs two key physiological functions: (1) to store urine, and (2) void urine at an appropriate time. While these two functions seem simple, both processes exert prolonged stretch and compressive forces on the urinary bladder vasculature that are greater than those seen by vessels in any other hollow organ. To compensate for these forces, the urinary bladder vasculature has adapted several key features that maintain blood flow during bladder filling and prevent damaging pressure fluctuations during emptying. This chapter first describes key anatomical features of the urinary bladder vasculature and how these features aid in maintaining blood flow in the milieu of the functioning bladder. Next, we investigate the mechanisms regulating excitability of urinary bladder arterioles with emphasis on the development and regulation of myogenic tone. We then discuss the physiological significance and excitability of urinary bladder capillaries and venules, and their important roles in maintaining tissue perfusion. Finally, the functionality of the urinary bladder vasculature will be explored in terms of bladder dysfunction, to understand if lower urinary tract symptoms associated with disease can be considered vascular in nature. Also included are perspectives on the urinary bladder itself as a model for understanding ischemia/reperfusion injury and the possibility that the urinary bladder holds a key to mitigating deleterious effects that result when blood flow is occluded and rapidly restored to other organs.