When the sensitive nerve endings of the ERECT PENIS are being stimulated, the BRAIN sends signals to the man’s REPRODUCTIVE SYSTEM that it is time to prepare for ORGASM and EJACULATION.

Muscles in the EPIDIDYMIS dump SPERM into the VAS DEFERENS, and it is then conveyed past the PROSTATE GLAND and SEMINAL VESICLES where fluids are added to produce SEMEN.

The SEMEN travels through the URETHRA to the internal base of the PENIS.

Beneath the CORPORA CAVERNOSA , the pair of spongy-tubes that make up the body of the PENIS and which, when filled with bl00d, cause an ERECTION, lies a third, softer tube of tissue called the CORPUS SPONGIOSUM. It houses the URETHRA as it passes through the PENIS, and its upper end makes up the internal structure of the GLANS. The back end of the CORPUS SPONGIOSUM extends into the man’s pelvic region and it flares to form a structure called the URETHRAL BULB.

SEMEN fills the URETHRAL BULB as stimulation of the PENIS continues. It can swell to two or three times its normal size during this process, which explains the “build up of pressure” a man feels as ORGASM approaches.

Once the “point of no return” arrives, the brain signals a pair of muscles, one completely surrounding the swollen URETHRAL BULB and the other surrounding the URETHRA itself, to contract in rhythmic unison to forcefully pump the SEMEN through the SHAFT of the PENIS and out of the MEATUS. (Much like squeezing the bulb of a turkey baster!).

Each contraction of those muscles is followed by a short period of relaxation, which allows the URETHRAL BULB to refill with SEMEN before the next pulse of the EJACULATION.

FUN FACT: It has been estimated that during EJACULATION SEMEN is propelled through the PENIS at approximately 11MPH!

You’re welcome,
Will