Self Cleaning Spiral Pee Stream

In the male urethra, a spiral stream of urine flows out through the external urethral meatus and effectively cleans the opening as it passes. Anatomists note that the urethral lumen runs parallel to the penis and then turns vertically at the narrow external meatus, a shape that produces this swirling stream and its self-flushing effect. Because the female urethra lacks an equivalent mechanism, bacteria have an easier path to the bladder, which partly explains why urinary tract infections occur much more frequently in females.

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