Micturition

Question 0

Describe in general the innervation of the bladder

Answer 0

Vesical nervous plexus
Motor innervation - sympathetic fibres
Internal urethral sphincter - autonomic
External urethral sphincter - somatic

Question 1

Describe the anatomy of the bladder

Answer 1

A hollow, muscular and distensible organ
Found in true pelvis
Detrusor muscle - layers in three directions (inner longitudinal, middle circular, outer longitudinal)
Smooth muscle - circular, longitudinal, spiral fibres
No peristaltic action

Question 2

Describe the normal voiding reflex of the bladder

Answer 2

Micturition neurones
Mediated by parasympathetic (S2-4)
Lateral horn of sacral cord –> Nervi erigentes
Cerebral cortex –> pons (M region) –> parasympathetic outflow (sacral) –> contraction of detrusor muscle, increase in intravesical pressure, relax external sphincter

Question 3

Describe the normal storage function of the bladder

Answer 3

Continence neurones
Storage for many hours (~550ml capacity)
As bladder fills, rugae flatten
At around 400ml, signal need to void
Bladder pain is not referre
Cerebral cortex –> pontine continence (L region) –> sympathetic nuclei –> relax detrusor muscle, increase external sphincter pressure