1. Excitement

The Scrotum
At the same time, the smooth muscles of the scrotum contract, its tissue thickens, and the testicles are pulled upward toward the abdomen by the contracting spermatic cords.

Muscular Tension, Pulse Rate and Blood Pressure
As sexual excitement increases, there is a corresponding increase in muscular tension. At the same time, the pulse rate and blood pressure rise.

Sex Flush
A number of men also experience what is known as a sex flush, i.e., a red rash that usually begins in the area of the lower abdomen and then spreads to the neck and face or even to the shoulders, arms, and thighs. The sex flush may start only late in the excitement phase and is more likely to appear in the plateau phase. In many cases, however, there is no sex flush at all.

Erection of Nipples
Not all males experience an erection of their nipples. In some men, it may be brought about by a direct stimulation of the breasts. When nipple erection occurs, it usually appears toward the end of the excitement phase or during the plateau phase and then lasts through the other phases.