20 Functions of the Foreskin
This list is intended to be exhaustive (including all functions, no matter how trivial, just as the most trivial of reasons to circumcise is taken seriously), in descending order of importance in each section.
Sexual
1
Erotic pleasure, especially via the ridged band and Meissner's corpuscles
2
Acts as a rolling bearing in intercourse and masturbation
3
Prevents dyspareunia (painful intercourse)
4
Stimulates partner's genitalia, giving erotic pleasure
5
Supplies skin to cover the shaft in erection and prevent tightness
6
Stores pheromones and releases them on arousal
7
Stores, releases and helps distribute natural lubricants ("smegma" and pre-ejaculatory fluid)
8
Makes the glans a visual signal of sexual arousal
9
Provides a seal against the vaginal wall to contain semen
Protective
10
Prevents the glans becoming keratinised, and keeps it soft and moist
11
Protects the thin-skinned glans against injury
But you know what happened to me when I was 10 years old? I was playing on a playground and slipped down a wet slide backwards. I landed facedown at the bottom. The ground was covered in rocks there from someone who had dumped a pile at the bottom of the slide. I scratched up my legs and stomach and tore my penis skin. It was hanging almost from a strand. The doctor made sure it was clean and sealed it with glue. Do you know what he said to me? He said, "If you were missing your foreskin, you would be having cosmetic surgery right now." My penis skin saved me from surgery!
12
Protects the nerves of the glans, retaining their erotic function
13
In infancy, protects the urethra against contamination, meatal stenosis, (and UTIs?)
14
Provides lysosomes for bacteriostatic action around the glans
15
Pigmented, it protects the unpigmented glans against sunburn
16
Vascular (rich in blood vessels that bring heat to the tissues), it protects the less vascular glans against frostbite, as Sir Ranulph Fiennes found on his epic transpolar walk.
Other
17As a tag with which to pull the penis out through the fly
18
Provides skin for grafts to burnt eyelids, reconstructive surgery, etc.
... to close an ulcer on his shin, caused by an auto accident. ...
Hawaiian_Gecko in the Washington Post, December 28, 2013
19 Provides sensitive skin to line the vagina in male-to-female sex-reassignment surgery
20
"The foreskin is important embryologically in the formation of the end of the penis and the urethra. If there is no foreskin the urethral opening is not at the end of the penis where it should be, but somewhere on the underside of the penis (hypospadius [sic])." - Dr Edgar Schoen (!) (but he claims that is its only function)