Male Reproductive System & Genital Anatomy


There are many features – pleasurable and functional – to male genital anatomy. Let’s go through some of the main parts, which you can see illustrated in the diagram below:


Penis: aka cock, dick, prick, wang…  oh hell, just watch this Austin Powers clip. OK, so the penis is the male’s external sex organ, which serves reproductive, functional (urination), and pleasurable purposes. Penises usually measure between 4.2 and 7.5 inches in length and 4 to 5 inches in girth (circumference) when erect (when the penis becomes firmer and bigger because of arousal). Some guys are smaller, some guys are bigger. Maybe you’ve heard the expression, “I’m a grower, not a show-er,” that’s when a guy’s penis starts out small and gets a lot bigger when he gets an erection.

Side note: just like how women can be concerned about the size, shape, and color of their breasts and labia, men can be concerned about the appearance of their penis. The truth is that penises have a lot of variation, not just in their length, girth, or coloring, but in the size of the glans (aka head), curve, and skin texture (click here to see the Soft/ Hard Gallery of photos showing what various penises look like in resting and erect states). Just like many men have a preference about the proportions of a woman, breast size, or some other physical feature of their partner, your partner may prefer a certain penis size. Social conditioning has something to do what we find attractive, but even without the influence of media it’s normal for people to be attracted to certain features or have specific preferences about those features. If you took a survey of men’s preferences of breast size, the most popular choice is a C cup, which is the average size of breasts. Likewise, if you took a survey of women’s preferences for penis size, most will mention that they care more about girth than length and would choose a penis of average length and girth, though some will choose a larger penis and a few will choose a smaller penis. At the end of the day, it’s all about loving what you’ve got and knowing how to use it. Keeley discusses penis size in more depth in her post.

Back to anatomy. The main parts of the penis, which you can see in the photo below, are the root (radix), the body (corpus), and the epithelium (skin tissue), which includes the shaft skin and the foreskin covering the glans. The body of the penis is made up of three columns of tissue: two corpora cavernosa (sponge-like tissues that contain most of the blood during an erection) on the dorsal side (top side) and corpus spongiosum (spongy tissue surrounding the urethra) between them on the ventral side (underneath). The urethra passes through the prostate gland, where it is joined by the ejaculatory duct, and then through the penis. The urethra moves across the corpus spongiosum, and the meatus (opening) lies on the tip of the glans. Read more about the penis here on Wikipedia.


Scrotum: not to be confused with testicles, the scrotum is the wrinkly dual-chambered sac of skin and muscle sectioned off by a septum (a dividing wall) that contains the testicles. Because higher temperatures may be damaging to sperm count, the scrotum keeps the temperature of the testes slightly lower than that of the rest of the body (35-36° Celsius or 95-96.8° Fahrenheit vs. a normal body temperature of 37° Celsius or 98.6° Fahrenheit). The temperature is controlled through the contraction and relaxation of the cremaster muscle in the abdomen and the dartos fascia (muscular tissue under the skin)  to move the scrotum closer to the body in a cool environment and farther away when it is hot. Moving the testes away from the body increases the exposed surface area, which allows excess heat to be dispersed. This is also why one side of the scrotum typically hangs lower than the other. Below is a photo of the scrotum reacting to a warm (left) and cool (right) environment.


What the guy is tugging on in the photo above is his foreskin: the fold of skin that covers the glans and opening of the penis when it is flaccid. Some men have their foreskin removed (usually when they are babies), which is called circumcision. While a common practice, many have compared it with female genital mutilation. Others say it is safer to remove the foreskin because it is easier to clean and less prone to infection and STDs. While still others just consider circumcision to be a part of their culture. When erect, an uncircumcised penis and circumcised penis are nearly identical looking and feeling. But they look and feel different when flaccid (not erect); the illustration below shows the difference.


Testicles: aka testes, testis, or “the balls”, are the ball-shaped organs inside the scrotum that are composed of coiled structures called seminiferous tubules, which is where sperm is produced. The sperm are then stored in the structure above the seminiferous tubules inside the testes called the epididymis. Vas deferens is the ejaculatory duct that carries the sperm from the epididymis to the ampulla in anticipation of ejaculation. During ejaculation, the sperm is propelled forward through the ejaculatory ducts to combine with semen from the prostate gland, and into the urethra, where the semen (containing the sperm) is ejected from the opening of the urethra at the tip of the penis. After being ejaculated into a woman, sperm can potentially fertilize an ovum (egg) in her body. The fertilized ovum (called a zygote) develops into a fetus (baby).

Want to learn more about how sperm can fertilize an egg? Watch this video:

Endocrine disruption resulting from chemical exposure (like pesticides, drinking from plastic water bottles containing BPA, or using plastic toys, equipment, or cosmetics that contain phthalates) has been linked to genital deformation and decreased penis size and sperm count (among many other problems). Diets high in soy and meats containing growth hormones have also been shown to decrease testosterone and sperm count. It is estimated that men today have 1/3 to 1/2 of the sperm count that their grandfathers had.

Semen: aka seminal fluid, semen is the sperm containing fluid that is discharged from the penis upon ejaculation. A typical ejaculation contains hundreds of millions of sperm. Semen originates from the seminal vesicle in the pelvis.

Urethra: a tube that connects the bladder to the tip (meatus) of the penis, where it opens and allows urination (pee) to come out. Women only use their urethra for urination, but men use their urethra for both urination and ejaculation.

Corona: refers to the raised rim around the circumference of the glans, it is highlighted in the photo below.

glans corona

– Perineum: the area of skin between the scrotum and the anus.

– Anus: is the opening to the rectum where feces exits the body, and connects internally to the large intestine. The anus is also the opening where prostate massage, or anal sex (for gay or bisexual men), takes place.

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