Semen is the thick, whitish mixture of fluids consisting of sperm
At the time of ejaculation, sperm leave the penis in semen.
Semen contains secretions of the male accessory reproductive glands (seminal vesicles, prostate gland, and the bulbourethral gland)
SEMINAL VESICLES - Paired seminal vesicles are glands on the posterior base of the urinary bladder; contribute nutrients and produce seminal fluid (fructose and seminal fluid) to semen; contribute approximately 60% of the semen volume
PROSTATE GLAND - This accessory reproductive gland, located around the male urethra below the urinary bladder also produces and adds a fluid to semen
BULBOURETHRAL GLAND - The pea-sized small bulbourethral glands, located below the prostate gland on either side of the urethra in males secretes mucus-containing fluid to semen; makes the seminal fluid gelatinous
Thus together, sperm and these secretions form a fluid called semen.