How do webs come out of spider-mans wrist?

Answer 1

In the comic books, Spider-Man's webs are shot out of mechanical devices called web shooters. In the movies, the webs were organic in nature, ie they came from his body. It was a part of the genetic mutation Peter Parker underwent after he was bitten by the radio active spider. Along wiht the ability to spin a web, the mutations gave him heightened reflexes, increased strength, increased durability, the ability to crawl up walls and "spider sense".

Answer 2

its a complicate answer but...

He made a sticky liquid that sticks to until any surface that hardens with the air contact and they go out because of a pressure mechanism (the wed-shooters themselves) that by pressing a button can throw this liquid that with the air contact hardens but having the same flexibility of a real spiderweb.

P.D.

This liquid is organic and disolves in a few hours

In Ultimate Spiderman it was first thinked (but not completely done) by his father

Answer 3

In the comic books Spiderman either wears his "webshooters" outside of his suit, or has small holes in the wrists of his suit. This allows him to shoot webbing all the while having his suit on to protect his identity.