Changes

The double-layered design of the [[foreskin]] does indeed permit smooth penetration and a sliding action. The [[skin]] of the penis, including the foreskin, becomes rougher during [[erection]]. This roughness is brought about by a mechanism similar to that which raises goosebumps. The extra frictional resistance brought about in this way reduces slippage of [[penile skin]] against female tissues. The double-layering of the foreskin is designed to offset the frictional effect of erect [[penile skin]] and allow for easy vaginal penetration.

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