The bladder neck is the region where the bladder connects to the urethra, playing a crucial role in urinary continence by maintaining closure during bladder filling and opening during urination. Its function is supported by the internal urethral sphincter, which is composed of smooth muscle fibers that contract involuntarily to prevent urine leakage.

Bladder Neck

Urinary continence is the ability to control the release of urine from the bladder, which involves a complex interaction between the central nervous system, the urinary sphincters, and the bladder muscles. Disruptions in this control can lead to urinary incontinence, a condition that affects quality of life and may require medical intervention.

Urinary Continence

Closure during bladder filling

Opening during urination

The internal urethral sphincter is a smooth muscle structure located at the junction of the bladder and urethra, playing a crucial role in the involuntary control of urination by maintaining urinary continence. It is innervated by the autonomic nervous system, which regulates its contraction and relaxation in response to bladder filling and voiding signals.

Internal Urethral Sphincter

Smooth muscle fibers are non-striated, involuntary muscles found in the walls of hollow organs, such as the intestines and blood vessels, responsible for regulating internal movement and flow. Unlike skeletal muscle, they contract slowly and can sustain contractions for extended periods without fatigue, playing a crucial role in maintaining physiological homeostasis.

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