The anatomy of the male urethral sphincter is complex and has been debated for over 150 years. It includes smooth muscle components like the internal urethral sphincter and striated muscle components like the external urethral sphincter. Recent studies using 3D modeling confirm that the bladder neck and proximal urethra include smooth muscle that acts as a sphincter to aid in continence, separate from the striated external urethral sphincter located further distally in the urethra. Proper continence requires coordination between these internal and external sphincter components as well as their innervation by the autonomic nervous system.
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