The Male Genital System

The male genital system consists of external and internal male sex organs. Hormones drive the entire male reproduction system.

The External Male Genital System

Most of the male genital organs are located outside the body, i.e. the penis, testicles, and scrotum.

Drawing male genital system
Courtesy of: Wikimedia commons


The penis has two functions, to allow you to empty your bladder and to have sexual intercourse (to reproduce). The penis consists of three parts, the penis root, shaft and glans.

The penis root is the embedded part of the penis, i.e. where it is attached to the pubic bone. The penis root serves as a base or support.

Actually, the penis is much longer than we see as half of the penis length is inside the body. MRI photos show that healthy erect penis is shaped like a boomerang.

The penis shaft (penis body) has cylinder shape. Inside the penis are three circular shaped chambers made of special sponge like tissue that fills with blood when men are sexually aroused. The skin is loose and elastic to accommodate the changes in the penis size during erection.

The penis glans (penis head) is the cone shaped part at the end of the penis. At the tip of the penis is the opening of the urethra, i.e. the tube that transports the urine and semen.

The penis head is enclosed by foreskin. Around one third of all men are circumcised, meaning the foreskin has been surgically removed.


Testicles (testes) are small oval shaped organs that are contained in the scrotum (the sac of skin that hangs below the penis). Most men have two testicles but their purpose is to produce sperm and testosterone, the primary male hormone.

The testicles play fundamental role in the male reproduction system, i.e. allowing you to get erection (testosterone) and father a child / reproduce (sperm).


Scrotum is the loose sac of skin that hangs below the penis and contains the testicles. It also contains nerves and blood vessels and acts as heat control system for the testicles.

The temperature in the scrotum is slightly lower than the body temperature, this is fundamental for healthy sperm production. The scrotum constantly monitors temperature changes in the environment and responds automatically to any changes, i.e. special muscles move the testes closer to the body if it is cold but farther away from the body when hot.

The Internal Male Genital System

The external male genital organs are visible and therefore well known. Important part of the male genital system is however inside the body.


The epididymis is a firm tube that lies on the back surface of each testicle. The epididymis plays various roles in the male reproduction system.

It transports and stores the sperm cells produced in the testicles. The sperm is however immature and not capable of fertilization when it comes from the testes so the epididymis is responsible for the final sperm maturation.

Vas Deferens

The vas deferens is a long muscular tube that connects the epididymis with the urethra. When men are sexually aroused, contractions force the sperm from the epididymis into the vas deferens, which transfers the mature sperm to the urethra in preparation for ejaculation.

Seminal Vesicles

The seminal vesicles are sac like pouches that are attached to the vas deferens near the base of the bladder.

The seminal vesicles secrete thick fluid that constitutes the bulk of the seminal fluid (semen).This fluid nourishes the sperm so it can move. The fructose in the fluid is the main energy source for the sperm outside the body.

Ejaculatory Ducts

The ejaculatory ducts are the coming together of the vas deferens and seminal vesicles. This is the interface between the reproductive and urinary systems and delivers sperm into the penis, prior to ejaculation.


The urethra is the tube that carries urine from the bladder, as well as ejaculating semen. The flow of urine is blocked from the urethra when the penis is erect, i.e. allowing only semen to be ejaculated during orgasm.

Prostate Gland

The prostate gland lies just beneath the bladders and the urethra runs through the middle of it. It is partly muscular and partly glandular and is the size of a walnut.

The main function of the prostate gland is to secrete slightly alkaline fluid that protects and enriches the sperm and forms part of the seminal fluid. During orgasm, the muscular glands help to push the prostate fluid into the urethra (in addition to the sperm that was produces in the testes).

Bulbourethral Glands

The bulbourethral glands (or Cowper's glands) are pea-sized glands that lie on each side of the urethra below the prostate gland.

The fluid produced by the bulbourethral glands is clear and thick. It acts as lubricant for the urethra, as well as flushing out the urethra before the semen is ejaculated, i.e. by neutralizing any acidity from the urine. It also makes the semen less watery.

Sex Hormones

Sex hormones drive the entire male reproduction system. Hormone is a chemical released by a cell or a gland in one part of the body that regulate the activity of cells or organs in other parts of the body, including in male genital system.

The primary male sex hormone is testosterone. It is mostly secreted in the testicles but the amount of testosterone is regulated by the hypothalamus and the pituitary gland.

Testosterone is responsible for the development of male characteristics, like muscle mass and strength, bone mass, fat distribution, voice change and facial hair growth.

Testosterone also stimulates sperm production and plays key role in the growth and maturation of the prostate gland and other male sex organs.

Testosterone level affects the sex drive (libido) and sexual function.

Other important male sex hormones include follicle-stimulating hormone, which stimulates the production of sperm and luteinizing hormone, which stimulates the production of testosterone.

The male genital system is more complex than it may seem at first. Knowing how the male genital system works can help you to stay fertile and sexually active for longer.