Final answer:
The first event in the male sexual response identified by the nurse is the excitement phase, characterized by vasodilation and vasocongestion in the erectile tissues leading to penile erection.
Step-by-step explanation:
The nurse would identify that the first event in the physiology of the male sexual response is the excitement phase. During this phase, vasodilation occurs causing vasocongestion in the erectile tissues.
Specifically, in males, the excitement phase is marked by the engorgement of the with blood due to the filling of erectile tissue structures such as the corpora cavernosa and corpus spongiosum. This vascular response leads to an erection, which is the visible sign of sexual arousal and the prerequisite for coitus.