When a man is sexually stimulated, friction on the glans penis and other stimuli send signals through the nervous system that result in ejaculation.
At the moment of ejaculation the walls of the epididymis contract (squeeze) to create peristaltic waves that push sperm into the vas deferens. Nerves also stimulate the seminal vesicles and the prostate to contract which forces semen (the mixture of sperm and secretions) into the urethra.
Muscles surrounding the urethra contract and propel semen out of the penis. To prevent semen from flowing backwards into the bladder, the muscles in the neck of the bladder tighten to close it off.
Side view of male reproductive system
Possible problems with ejaculation include:
- premature ejaculation;
- delayed ejaculation; and
- retrograde ejaculation.