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Ejaculation
Ejaculation, controlled by the central nervous system, happens when sexual stimulation and friction provide impulses that are delivered to the spinal cord and into the brain.
Ejaculation has two phases:Phase I: Emission
The vas deferens (the tubes that store and transport sperm from the testes) contract to squeeze the sperm toward the base of the penis through the prostate gland. The seminal vesicles release secretions that combine with the sperm to make semen. The ejaculation is unstoppable at this stage.
Phase II: Ejaculation
The muscles at the base of the penis contract forcing semen out of the penis (ejaculation and orgasm) while the bladder neck contracts. Orgasm can occur without the delivery of semen (ejaculation) from the penis. Normally, erections are lost following ejaculation.
