1, penis composition The penis is divided into three parts: head, body and root. The front enlarged part of the penis is the head of the penis, and there is an external urethral opening at the tip of the head. The middle part is the penis body, which is cylindrical and hangs below the front of the pubic symphysis and is the moveable part. The posterior end is the root of the penis, which is hidden in the deep surface of the scrotum and the skin of the perineum, and is fixed to the subpubic and sciatic branches. The penis is composed of two corpus cavernosum and one urethral corpus cavernosum, covered with fascia and skin. The outer layer of each corpus cavernosum is covered with a tough fibrous membrane, called the white membrane of the penile corpus cavernosum and the white membrane of the urethral corpus cavernosum, respectively (Figure 1-1 and Figure 1-2). Figure 1-1 Penile column-like structure Figure 1-2 Penile section 2, the principle of penile erection As the name suggests, the penile corpus cavernosum is like a sponge inside and consists of many cavernous trabeculae and cavities, which are actually sinus gaps connected with blood vessels. When these cavities are filled with blood, the penis becomes thicker, harder and induces an erection. Conversely, it becomes thinner and weaker. When the penis is not erect, the blood flow through the corpus cavernosum is very small, about 4 ml per minute, and the whole penis is in a weak state. When sexually aroused, the cavernous body of the penis is filled with blood and therefore erect, the blood flow can suddenly increase to 80-120 ml per minute, an average of 100 ml. Even after a full erection, in order to maintain this erect state, it is still necessary to have 20-40 ml of blood flow per minute into the cavernous body of the penis, so as to maintain the penis firm. With this increased blood flow, the pressure inside the sponge suddenly increases and the penis erects and becomes hard. The reasoning behind an erection is similar to that of an inflated tire; when there is enough air, the tire becomes hard. Of course, the mechanism of penile erection is much more complicated than tire inflation, which requires a dynamic balance of constant filling of the cavernous body and blood return, thus always maintaining the proper pressure in the cavernous body of the penis to maintain the erect state and erect hardness. In short, the main factor affecting the degree of hardness of the penis after erection is the balance between the inflow and outflow of penile blood flow. 3.Introduction of penile support body The penile support body is commonly known as “three pieces” and consists of three parts: fluid pump valve, fluid capsule and cylinder (Figure 3-1). The two cylinders of the support body are placed in the two penile cavernous cavities to support the erection of the penis; a fluid capsule is placed in the posterior pubic space as a fluid source; a fluid pump valve (control switch) is placed in the scrotum, and the patient can freely control the erection and weakness of the penis, and regulate the hardness and duration of the penis by hand. The “three-piece set” simulates the erection and weakness of the penis in a physiological state. The patient can also have orgasm and ejaculation during sexual intercourse after the prosthesis, and the normal urinary function is not affected, and the appearance of the penis is basically the same as before the surgery. Figure 3-1 Diagram of penile support body