环的作用一样吗？
作为环学家，可以明确的告诉你，不同类型的环作用是不同的！ 1. 节育环（女用） 原理：机械性阻塞宫腔，阻止胚胎着床或发育成胎儿。有些含铜、含药的节育环还可达到避孕效果。 类型及功能： 带尾丝的节育环(instrumented IUD) 这种IUD在宫颈口上有一个“尾巴”，脱落后进入腹腔，医生可借助光学器械找到其位置并予以取出； 带铜IUD(C-IUD)， 在子宫腔内通过缓慢释放铜离子而达到避孕效果，是目前国内应用最广的一类节育环，分不带尾丝和不带尾丝两种类型。 不带尾丝型节育环 C-IUDs are the most widely used kind of intrauterine device in China， with or without an inserted metal wire (see Fig. 2). They contain a rubber stopper at their open ends to prevent inadvertent expulsion and a copper tube wrapped around one or both sides of the plastic frame. The tube is filled with either progestogen or estrogen/progestogen mix. Inhibiting ovulation by changing the cervical mucus so that sperm cannot move towards the egg， blocking the tube through which the egg travels from the womb to the egg; and preventing implantation if necessary by slowing down the womb contractions during the first few days after fertilization. All these functions are achieved by the gradual release of metals， such as copper and silver——which are highly toxic to human eggs and embryos——from the device over several years. Because they work mainly on metabolic level， C-IUDs are considered nonhormonal.
2. 绝育环（男用） 原理：阻断输精管，造成精子不能输出而导致不育。
3. 异位环（男女均可） 原理：将环植入子宫腔内一定的部位，当受精卵着床时，由于环的存在而阻碍着床，从而起到避孕作用。 目前临床使用较少。