The sympathetic nervous system innervation for the internal urinary sphincter originates from which spinal cord levels?

The sympathetic nervous system innervation for the internal urinary sphincter originates from which spinal cord levels?

• A. S2-S4
• B. C3-C5
• C. T10-T12
• D. L1-L3

Answer: (C)

Sympathetic control of the internal urinary sphincter comes from the thoracolumbar outflow, which keeps the sphincter contracted during urine storage. The preganglionic neurons that provide this sympathetic input are located in the intermediolateral cell column of spinal cord segments around the lower thoracic to upper lumbar levels, commonly described as roughly T10 to L2. From there, fibers travel through the sympathetic chain to hypogastric pathways and reach the internal sphincter to maintain closure. Therefore, the level range that matches this sympathetic supply for the internal urethral sphincter is the one that contains those thoracic-to-upper-lumbar segments, which is T10–T12 in the given options. This is distinct from parasympathetic input (pelvic splanchnic nerves from S2–S4) that promotes detrusor contraction and sphincter relaxation during voiding, not maintenance of continence.

Sympathetic control of the internal urinary sphincter comes from the thoracolumbar outflow, which keeps the sphincter contracted during urine storage. The preganglionic neurons that provide this sympathetic input are located in the intermediolateral cell column of spinal cord segments around the lower thoracic to upper lumbar levels, commonly described as roughly T10 to L2. From there, fibers travel through the sympathetic chain to hypogastric pathways and reach the internal sphincter to maintain closure.

Therefore, the level range that matches this sympathetic supply for the internal urethral sphincter is the one that contains those thoracic-to-upper-lumbar segments, which is T10–T12 in the given options. This is distinct from parasympathetic input (pelvic splanchnic nerves from S2–S4) that promotes detrusor contraction and sphincter relaxation during voiding, not maintenance of continence.