Micturition

The bladder has a dual function. For most of the time it is a compliant muscular organ that stores up to 1 litre of urine. It is therefore important that the intravesical pressure is less than that of the upper tract to allow filling. Its second function is to facilitate controlled voiding and for this purpose a sufficient intravesical pressure must be generated to overcome the resistance of the outflow tract. Micturition requires that the lower urinary tract undergoes two coordinated processes: reduction of bladder outflow resistance and an increase of bladder vesical pressure. Normal micturition is impossible if these two processes do not occur together.