1. Erection, Orgasm, and Ejaculation
Sexual stimulation leads to parasympathetic nerve impulses from the spinal cord to release NO, a vasodilator.
Arteries leading to the penis dilate.
Pressure from arterial blood filling the vascular spaces of erectile tissue compress the penis veins.
Venous blood cannot flow out of the penis, erectile tissue fills, and an erection is produced.

2. Erection, Orgasm, and Ejaculation, continued…..
Emission and ejaculation accompany male orgasm.
Emission: the movement of sperm cells from the testes and secretions from the prostate gland and seminal vesicles into the urethra.
Ejaculation: the process of forcing semen through the urethra to the outside

3. Erection, Orgasm, and Ejaculation, continued…..
Emission and ejaculation events occur so that:
Fluid from bulbourethral glands is expelled first
Fluid from the prostate gland is released next
Then sperm cells
Lastly, fluid from the seminal vesicles

4. Erection, Orgasm, and Ejaculation, continued…..
Following ejaculation:
Arteries that supply erectile tissue contract,
Veins of the penis “drain” the spaces of the erectile tissue,
Penis returns to flaccid state