Male reproductive system: Structure and function

The male reproductive system consists of external sex organs, which include the penis and the scrotum, and internal sex organs, which include the testicles, the epididymis, and the vas deferens. Internal sex organs also include the male accessory sex glands: the seminal vesicles and the prostate gland.

First, let’s focus on the external sex organs. The penis has three main parts: the root, the body, and the glans, which is covered with a fold of skin called foreskin, or prepuce.

At the top of the glans is the opening of the urethra, which is a tube that carries urine and sperm outside of the body.

If we do a cross-section of the penile body, you can see two columns of erectile tissue called corpora cavernosa. Corpora cavernosa fills with blood and enables an erection.

On the other hand, there’s also a spongy tissue around the urethra, called corpus spongiosum. During an erection, corpus spongiosum fills with a small amount of blood to prevent the compression of the urethra.

Below the penis is a pouch that contains testicles, called the scrotum. The scrotum hangs outside of the body keeping the temperature of the testicles about three degrees lower than body temperature. This is the perfect environment for testicles to produce sperm.

Besides sperm, testicles also produce testosterone, which is a hormone that is responsible for the normal development of male secondary sex characteristics, such as the growth of body and facial hair, changes in body form, and lowered voice pitch.

Now, sperm production, also known as spermatogenesis, begins in puberty in biological males and continues throughout the lifetime. But, sperm cells that are produced in testicles are actually immature.

From the testicles, immature sperm cells travel to the epididymis, which is a coiled tube structure, where they mature and gain the ability to move on their own.

From this moment on, sperm cells are able to “swim” to the egg in the female reproductive tract and fertilize it. During ejaculation, maturated sperm cells exit the epididymis and enter the 30-cm long tube called the vas deferens.