Micturition

Micturition is the process of emptying the urinary bladder. It´s foundation is micturition reflex which is an autonomic spinal cord reflex. Despite being autonomic, it can be affected (facilitated or inhibited) by centres in brainstem and cerebral cortex.

The micturition is based on the contraction of the smooth muscle of the urinary bladder (m. detrusor) and synchronized relaxation of the two sphincters of urethra – internal (smooth muslce) and external (skeletal muscle). Furthermore the relaxation of the muscles of the pelvic floor takes place.

Micturition reflex
The increased volume of the urinine in the urinary bladder is registered by mechanoreceptors located in it´s wall.

Afferent pathway is mediated via pelvic nerves. They bring the signal to the center of the reflex in sacral spinal cord.

Efferent pathway is executed via sacral parasympathetic nerves that are also part of the pelvic nerves. These nerves innervate m. detrusor (contraction) and m. sphincter urethrae internus (relaxation).

In order to achieve micturition (emptying the urinary bladder) the m. sphincter urethrae externus has to be relaxed consciusly. The relaxaion of the outer sphincter is initiated in cerebral cortex and executed via pudendal nerves. The micturition reflex can be triggred even when the urinary bladder is empty.

Micturition disorders

 * dysuria;
 * nykturia;
 * stranguria;
 * polakisuria.