The Male Reproductive System

The testes are the male primary sex organs, or gonads. They are suspended outside the body in a scrotal sac, where the slightly cooler temperature is essential for allowing spermatogenesis, or the synthesis of sperm, to occur. In addition to sperm production, which occurs in the seminiferous tubules, the testes are also the site of sex hormone synthesis.

Once the sperm leave the testes, they pass through a series of ducts. In sequential order these are the epididymis, the ductus deferens and the urethra. It takes about 20 days for the sperm to pass through the epididymis, and during this time the cells mature and develop the ability to swim. During ejaculation, the thick muscular walls of the ductus deferens contract to propel sperm from their storage site in the epididymis into the urethra. The urethra is the last part of the male duct system. It runs through the penis to convey both urine and semen to the outside of the body.

The penis has two principal functions; as a conduit for both sperm and urine, it acts as both the organ of copulation in the reproductive system and as an excretory organ in the urinary system.

The accessory glands of the male reproductive system include the paired seminal vesicles, the prostate gland, and the paired bulbourethral glands. The seminal vesicles secrete a yellow, viscous, sperm-activating fluid, which accounts for about 60% of the volume of the semen. The duct of the seminal vesicle fuses with the ductus deferens to produce an ejaculatory duct, where sperm and seminal fluid mix. The prostate gland surrounds the urethra as it exits the bladder. It contains 20-30 branched tubuloalveolar glands, which secrete their contents, a citrate and enzyme rich fluid, which makes up about a third of the semen volume, via excretory ducts into the prostatic urethra. The bulbourethral glands, also called Cowper’s glands, synthesise clear, thick mucus, which drains into the spongy urethra, lubricating it and neutralising any traces of acidic urine.