Changes

* When sexual receptivity of the female is established and sufficient arousal is accomplished in the male, erection and protrusion of the penis ensue.   

* When sexual receptivity of the female is established and sufficient arousal is accomplished in the male, erection and protrusion of the penis ensue.   

* Successful penile erection requires a complex series of neural and vasomotor reactions.   

* Successful penile erection requires a complex series of neural and vasomotor reactions.   

* Erection of the penis is necessary for copulation and deposition of [[Copulation_-Sperm_in_the_Female_Tract_- Anatomy & Physiology|semen in the female reproductive tract]].

* Erection of the penis is necessary for copulation and deposition of [[Sperm in the Female Tract - Anatomy & Physiology|semen in the female reproductive tract]].

* Erection is characterized by a marked increase in rigidity of the penis.

* Erection is characterized by a marked increase in rigidity of the penis.

* Increased rigidity is the result of increase in arterial inflow of blood compared to venous outflow.

* Increased rigidity is the result of increase in arterial inflow of blood compared to venous outflow.