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The membranous urethra passes through the urogenital diaphragm. It is the narrowest part of male urethra and is surrounded by the sphincter urethra muscle, which allows voluntary control of the bladder function.The spongy urethra is located inside the corpus spongiosum of the penis. The ducts of bulbourethral glands open into the proximal part of spongy urethra. The spongy urethra ends with the enlargement in the glans of the penis called the navicular fossa.
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