[Functional anatomy and semiology of the bladder]

Continence and micturition result from an inversely related evolution of urethra and bladder pressures. On filling, the bladder pressure remains low and the urethral pressure is high: filling bladder pressure mainly depends on its visco-elastic properties while urethral pressure is actively kept high by the tonic activity of smooth and striated urethral sphincters. It is the other, way round when the bladder empties: bladder pressure rises and urethral pressure lower, because the parasympathetic impulses; in the adult, the reflex loop passes through the pontine center. The volitional control of this micturitional reflex implies an ability to recognize a specific feeling: the desire to urinate. Physical examination and investigations enables to assess bladder and sphincter function, through a rich semiology.