To understand how sperm are released, one must know the functions of the male reproductive organs. The male reproductive system includes: testicles, urethra, vas deferens, prostate gland, seminal vesicle, and penis. The testicles are made up of seminiferous tubules, where sperm are formed. The structure located above the seminiferous tubules is called the epididymis. There, the spermatozoa mature and are then stored. To get an erection, first, the penis is filled with blood. Then, with sufficient stimulation, ejaculation begins. Mature sperm make their way from the epididymis, through the vas deferens, a muscular tube along which they move forward and which performs slight contractions. The spermatozoa reach the dilated part of the vas deferens, where the secretion from the seminal vesicle is added. The sperm then proceed through the ejaculatory duct and urethra, passing first through the prostate gland, where a milk-like fluid is added. This is how seminal fluid is formed. Finally, it is excreted through the urinary canal.