Changes

The term "'''Gliding action'''" is used to describe the way the [[foreskin]] moves during sexual intercourse. The foreskin is internally lubricated with body fluid, so it glides frictionlessly over the shaft and [[Preputial mucosa| inner layer]] of foreskin. This mechanism was described by Lakshamanan & Prakash (1980), stating that "[t]he outer layer of the prepuce in common with the [[shaft skin|skin]] of the shaft ]] of the penis glides freely in a to and fro fashion..."<ref>{{REFjournal

|quote=The outer layer of the prepuce in common with the [[shaft skin|skin]] of the shaft ]] of the penis glides freely in a to and fro fashion and has to be delicate and thin, as was observed in this study. [...] The inner lining of the projecting tubular part has the structure of the outer layer and adds to the thin gliding [[skin]] when retracted.

|quote=During intercourse, the natural penis shaft actually glides within its own shaft [[shaft skin]] covering. This minimizes friction to the vaginal walls and opening, and to the shaft [[shaft skin]] itself, adding immeasurably to the comfort and pleasure of both parties.<br>Friction is not entirely eliminated during natural intercourse but it is largely eliminated. Friction can take place in the lower vagina, but only if the man uses a stroke that exceeds the (forward and backward) gliding range of the [[shaft skin|shaft's extra [[skin]]. And in such a case, there will be friction only to the extent that the shaft exceeded its extra [[skin]], which is uncommon since the natural penis has a propensity for short strokes. Primarily, it is the penis head that makes frictional contact with the vaginal walls, usually in the upper vagina where there is ample lubrication. [...] The gliding principle of natural intercourse is a two-way street—the vagina glides on the shaft [[shaft skin]] while the shaft [[shaft skin]] massages the penis shaft as it glides over it.

Removal of the foreskin tightens the shaft [[shaft skin]] and reduces or eliminates gliding action. It also results in [[keratinization]] or callousing of the [[glans penis]] because of chafing and abrasion from clothing, leading to loss of sensation. Removal of the [[foreskin]] can lead to trauma of the penis (friction irritation) during [[masturbation]] due to the loss of the gliding action of the foreskin and greater friction, requiring the need of artificial lubrication. During sex, the loss of gliding action is also thought to cause pain, dryness, and trauma to the [[vagina]] of the female partner.<ref name="warren-bigelow"/> The trauma and abrasions of the vagina can lead to easier entry of [[Circumcision and STDs| sexually transmitted diseases]].<ref name="Bullough2014">{{REFbook