Bladder and Urethra

Sympathetic nerves to the bladder and urethra originate from the 11th thoracic to the 2nd lumbar segments, travel through the superior hypogastric plexus, and supply the bladder through the right and the left hypogastric nerves. ^[3] Parasympathetic nerves arise from the second through the fourth sacral segments and form the pelvic parasympathetic plexus, which is joined by the hypogastric plexus. Vesical branches then proceed toward the bladder base, where they provide the nerve supply to the bladder and proximal part of the urethra ( Fig. 54-2 ). Parasympathetic fibers are the main motor supply to the bladder (with the exception of the trigone) and hence far outnumber sympathetic fibers in the bladder.^[3]

The afferents carrying sensations of stretch and fullness of the bladder are parasympathetic, whereas pain, touch, and temperature sensations are carried by sympathetic nerves. Sympathetic fibers are predominantly α-adrenergic in the bladder base and urethra and β-adrenergic in the bladder dome and lateral wall. Knowledge of these aspects of neuroanatomy is important to appreciate the pharmacologic effects on the urologic system of neural ablation or regional block and drugs with adrenergic or cholinergic effects.^[3]