The inflatable penile prosthesis consists of two attached cylinders -- a reservoir and a pump -- which are placed surgically in the body. The two cylinders are inserted in the penis and connected by tubing to a separate reservoir of saline. The reservoir is implanted under the rectus muscles in the lower abdomen. A pump is also connected to the system and sits under the loose skin of the scrotal sac, between the testicles.
This penile prosthesis is referred to as a 3-piece inflatable penile prosthesis, due to the three different components. A 2-piece inflatable penile prosthesis consists of only two components: the attached cylinders and the combined reservoir and pump unit. Instead of the reservoir being placed behind the groin, it is combined with the pump into one housing unit that fits comfortably within the scrotum. The advantage of a 2-piece prosthesis in that the surgery is shorter and less complicated and there is no device parts in the abdomen. The disadvantage of the 2-piece prosthesis is that the smaller reservoir may not result in adequate erections in some men.
To inflate the prosthesis, the man presses on the pump. The pump transfers saline from the reservoir to the cylinders in the penis, inflating them and causing an erection. Pressing on a deflation valve at the base of the pump returns the fluid to the reservoir, deflating the penis and returning it to the normal flaccid state.