The most obvious physical sign of sexual arousal in men is erection of the penis. The increased blood flow into the penis causes it to stiffen. As the spongy tissue inside becomes filled with blood, pressure is put on the veins inside the penis which prevents blood from flowing out which helps to keep the penis hard. Once the penis has become erect, a few drops of clear, slippery fluid may come out of the tip of the penis. This is called lubricant or “pre-cum” and helps create less friction during sexual activity.
For men, orgasm occurs in two basic stages. In the first stage, semen flows to an area near the base of the penis. Once this happens, the man usually has a feeling that he is about to ejaculate. This is sometimes called “the point of no return” because once the semen has reached this area, the man will not be able to stop himself from ejaculating. In the second stage, the base of the penis and muscles in the pelvic area go through a series of contractions (5 to 8 on average), causing the semen to be pumped out of the penis. The semen may squirt or dribble out. During orgasm, a man’s body may stiffen up or he may have mild muscle contractions. Once he has finished ejaculation, his body will relax and the penis goes back to its usual size.