ABSTRACT
The urinary bladder is a unique organ. As a hollow structure, it demonstrates a remarkable integration of neuromuscular, mechanical, and physical properties that are crucial for its normal function. No other organ is evolutionarily programmed to fill with fluid over hours at low pressures, and then contract on demand to evacuate its contents. The bladder is the only autonomic organ under voluntary control. Indeed, the sociobiologic etiology and reasons for the existence of this unique behavior have been argued for decades. Although the ability to accommodate a fluid volume (filling) is thought to represent largely a passive phenomenon, this is not entirely the case. Recruitment of active neuromechanical properties is crucial for maintenance of low intravesical pressures during filling, and to this end the character of the surrounding cellular elements and extracellular matrix (ECM) can either facilitate or compromise this function. Bladder contraction (emptying), on the other hand, is largely an active neuromuscular process, although it is also influenced by the physicochemical nature of the ECM, and obviously depends on the overall mass and optimal functional status of bladder smooth muscle cells (bSMCs). This chapter reviews some of the biologic concepts related to normal bladder development and function, a complex orchestration of events that, if disturbed, can lead to a significant functional disharmony that places both continence and renal function at risk.
