12 Facts About the Penis

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Of all the body parts, none may elicit more questions—and myths—than the penis. One of the male sexual organ's main roles is to make procreation happen, but the penis also has cultural significance. Here are 12 facts to clear up the confusion.

1. THE PENIS HAS TWO PRIMARY FUNCTIONS.

The penis has two main biological roles, according to Michael Reitano, a physician-in-residence and an expert in sexual health and wellness for Roman Health. One is the elimination of waste in the form of urine; the second is the means for transferring semen, which carries sperm from the testes out of the body to somewhere else, such as the vagina for procreation. Another of its functions is, of course, sexual pleasure.

2. IT DEVELOPS FROM A CLITORIS-LIKE ORGAN.

All mammalian embryos start life as female in presentation, before the chromosome process is activated, with an external, undifferentiated clitoris-like structure. Eventually, embryos with XX chromosomes will develop a clitoris, labia, and vagina, while those with XY chromosomes will grow a penis and testes.

3. THE PENIS IS COMPOSED OF THREE TUBES.

The penis may look like one long tube, but there are actually three columns of tissue that run along the inside of the penis. Two are corpus cavernosum columns, which extend from the base to the end of the penis and fill with blood to allow for erection. The other is the corpus spongiosum; it surrounds the urethra, the tube through which urine and semen passes. The corpus spongiosum also fills with blood during erection, but remains pliable to keep the urethra open.

4. HUMANS MAY HAVE THE LARGEST PENIS OF ALL PRIMATES ...

When girth is considered, the human penis is quite a bit larger than those of its primate cousins. "A gorilla, for example, has a penis just 2 inches long. Human males walk upright, and it is thought that larger genitalia might have acted as a sexual attractant in competitive situations," Reitano says. But according to the Center for Academic Research and Training in Anthropogeny, chimpanzees and bonobos' penises are more slender but comparable to the length of an average human penis (which is 5.16 inches long and 4.59 inches around when erect, 3.61 inches and 3.66 inches around when not). Scientists theorize that our unique proportions are a result of natural selection through female mate choice.

5. ... AND THOSE PENISES MAY ONCE HAVE BEEN BARBED.

The human penis is most definitely among the smoothest in the animal kingdom. "In the distant past, it probably had sharp barbs, like some of our primate cousins, to make sex with another partner soon after coitus unlikely," Reitano says. Chimp penises still have small barbs that "hold the female in place, and when the penis is removed, it irritates the female's vagina so she avoids other chimps who might want to mate with her," he explains. (Let's not get started on the exploding corkscrew penis of the Muscovy duck, which looks like it makes for some irritating coitus.)

6. IN THE 15TH CENTURY, MEN FEARED WITCHES WHO COULD STEAL THEIR PENISES.

One of many bizarre beliefs put forth in the Malleus Maleficarum, a 15th-century German witch-hunting manual by Heinrich Kramer and Jacob Sprenger, was the opinion that witches could steal men's penises. Kramer wrote that witches "can take away the male organ." He didn't mean Lorena Bobbitt-style, clarifying, "not indeed by despoiling the human body of it, but by concealing it with some glamour."

In a 2002 paper published in the Journal of Folklore Research, Moira Smith pointed to male sexual insecurity as a driver of the witch hunts. "Many of the crimes (maleficia) attributed to witches concerned sexuality: copulation with incubus devils, procuring abortions, causing sterility and stillbirth, and impeding sexual relations between husbands and wives," she wrote.

7. ERECTIONS ARE MORE COMPLICATED THAN THEY SEEM.

Achieving an erection is one of the most complex functions to happen in a man, Reitano says: "For starters, hormones must be released on demand, arteries need to carry six times more blood to the penis with perfect efficiency, the nervous system must transmit its signals without a hitch, and the mind must be working in perfect harmony with the body."

The ability to get and sustain an erection, he says, depends upon "a body that is perfectly tuned physically, psychologically, and emotionally." The inability to achieve an erection, a.k.a. erectile dysfunction, is usually the first sign of poor health, according to Reitano.

8. UNLIKE OTHER MAMMALS, HUMANS LACK A PENIS BONE …

Many mammals, including gorillas and chimpanzees, have a penis bone or "baculum," says Arash Akhavein, a urologist at Cedars-Sinai in Los Angeles. In some animals, like whales, the baculum hangs back inside the abdomen until mating time, and then it slides into the penis to help maintain an erection. Instead of relying on this kind of structure, the human penis requires blood flow and engorgement for erection.

9. … AND YET IT'S POSSIBLE TO "FRACTURE" A PENIS.

Unfortunately, the penis can be fractured during sex, Reitano says. While penile fracture is relatively uncommon, it can happen when the thick sheath called the tunica albuginea, which gives an erect penis its rigidity, is injured by blunt force. "When it fractures, there is usually a clear popping sound, extreme pain, and the rapid loss of erection," Reitano says.

And yes, researchers have studied the sexual positions associated with the problem in heterosexual couples. A 2014 study in Advances in Urology found that the woman being atop the man was the primary position associated with penile fracture; the man being behind the woman was the second most commonly linked. A 2017 study in the International Journal of Impotence Research found that man-behind-woman was most often associated with fracturing a penis, followed by man-atop-woman.

10. MASTURBATION FEARS MAY HAVE DRIVEN MASS CIRCUMCISION.

In an uncircumcised penis, the glans (head) of the penis is covered by skin known as the foreskin, which can be pulled back from the glans. Circumcision, the removal the foreskin, is an ancient surgical practice performed for religious reasons and to prevent issues stemming from poor hygiene.

One thing circumcision doesn't prevent is masturbation. But in English-speaking countries in the 19th century, a general attitude against sexual profligacy, fueled by religious ideology, led to fears about the effects of masturbation and a spike in circumcision. Religious leaders and physicians warned people to avoid "self-abuse" for fear it could cause physical and mental disorders such as tuberculosis, memory loss, and epilepsy. As Tom Hickman writes in his book God's Doodle: The Life and Times of the Penis, "What made circumcision common among the proliferating 19th-century middle classes on both sides of the Atlantic was the hysteria about masturbation; removing the foreskin helped its prevention, doctors declared, and also cured bed-wetting and other conditions."

11. ADULT MEN GET CIRCUMCISED, TOO.

It's most common for boys to be circumcised as newborns, and in some cultures as adolescents, but there are a number of reasons why adult men may choose to have a later-in-life circumcision, Akhavein says. These include tears in the skin where the tip of the penis attaches to the foreskin; when the foreskin is too tight to be retracted easily, a condition called phimosis; and a buildup of smegma, a whitish waxy substance made up of dead skin cells and oils. Men who had an incomplete circumcision (too little skin removed) in childhood would also be good candidates.

12. ICELAND HAS A PENIS MUSEUM.

In 1974, an Icelandic history teacher named Sigurður Hjartarson received a cattle whip made out of a bull penis, which apparently gave him the idea to collect other penises, because hey, why not? The result is the Icelandic Phallological Museum, which holds a collection of more than 238 penises and penile parts from nearly all the fauna in Iceland. Yes, including Homo sapiens.

The largest penis on hand, from a sperm whale, stands at 6 feet tall and weighs nearly 150 pounds. "You’ll learn that as with everything in nature, the diversity in this department is as great as in any other; even within the same species the difference in size and shape is often quite remarkable," Hjartarson told Mental Floss in 2015.

10 Facts About Your Tonsils

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Most of us only become aware of our tonsils if they become swollen or infected. But these masses of lymphatic tissue in the mouth and throat are important immunological gatekeepers at the start of the airways and digestive tract, grabbing pathogens and warding off diseases before they reach the rest of your body. Here are some essential answers about these often-overlooked tissues—like what to do when your tonsils are swollen, and whether you should get your tonsils removed.

1. People actually have four kinds of tonsils.

The term tonsils usually refers to your palatine tonsils, the ones that can be seen at the back of your throat. But tonsillar tissue also includes the lingual tonsil (located in the base of the tongue), tubal tonsils, and the adenoid tonsil (often just called adenoids). "Collectively, these are referred to as Waldeyer's ring," says Raja Seethala, the director of head and neck pathology at the University of Pittsburgh Medical Center and a member of the College of American Pathologists Cancer Committee.

2. Tonsils are one of the body's first responders to pathogens.

The tonsils are a key barrier to inhaled or ingested pathogens that can cause infection or other harm, Seethala tells Mental Floss. "These pathogens bind to specialized immune cells in the lining—epithelium—to elicit an immune response in the lymphoid T and B cells of the tonsil," he says. Essentially, they help jumpstart your immune response.

3. Adenoid tonsils can obstruct breathing and cause facial deformities.

If the adenoid tonsils are swollen, they can block breathing and clog up your sinus drainage, which can cause sinus and ear infections. If adenoids are too big, it forces a person to breathe through their mouth. In children, frequent mouth breathing has the potential to cause facial deformities by stressing developing facial bones. "If the tonsils are too large and cause airway obstruction, snoring, or obstructive sleep apnea, then removal is important," says Donald Levine, an ear, nose, and throat specialist in Nyack, New York. Fortunately, the adenoids tend to get smaller naturally in adulthood.

4. As many of us know, sometimes tonsils are removed.

Even though your tonsils are part of your immune system, Levine tells Mental Floss, "when they become obstructive or chronically infected, then they need to be removed." The rest of your immune system steps in to handle further attacks by pathogens. Another reason to remove tonsils besides size, Levine says, is "chronic tonsillitis due to the failure of the immune system to remove residual bacteria from the tonsils, despite multiple antibiotic therapies."

5. Tonsillectomies have been performed for thousands of years ...

Tonsil removal is believed to have been a phenomenon for three millennia. The procedure is found in ancient Ayurvedic texts, says Seethala, "making it one of the older documented surgical procedures." But though the scientific understanding of the surgery has changed dramatically since then, "the benefits versus harm of tonsillectomy have been continually debated over the centuries," he says.

6. ... and they were probably quite painful.

The first known reported case of tonsillectomy surgery, according to a 2006 paper in Otorhinolaryngology, is by Cornélio Celsus, a Roman "encylopaediest" and dabbler in medicine, who authored a medical encyclopedia titled Of Medicine in the 1st century BCE. Thanks to his work, we can surmise that a tonsillectomy probably was an agonizing procedure for the patient: "Celsus applied a mixture of vinegar and milk in the surgical specimen to hemostasis [stanch bleeding] and also described his difficulty doing that due to lack of proper anesthesia."

7. Tonsil removal was performed for unlikely reasons.

The same paper reveals that among some of the more outlandish reasons for removing tonsils were conditions like "night enuresis (bed-wetting), convulsions, laryngeal stridor, hoarseness, chronic bronchitis, and asthma."

8. An early treatment for swollen tonsils included frog fat.

As early practitioners struggled to perfect techniques for removing tonsils effectively, another early physician, Aetius de Amida, recommended "ointment, oils, and corrosive formulas with frog fat to treat infections."

9. Modern tonsillectomy is much more sophisticated.

A common technique today for removing the tonsils, according to Levine, is a far cry from the painful early attempts. Under brief general anesthesia, Levine uses a process called coblation. "[It's] a kind of cold cautery, so there is almost no bleeding, less post operative pain, and quicker healing. You can return to normal activities 10 days later," Levine says.

10. Sexually-transmitted HPV can cause tonsil cancer.

The incidence of tonsillar cancers is increasing, according to Seethala. "Unlike other head and neck cancers, which are commonly associated with smoking and alcohol, tonsillar cancers are driven by high-risk human papillomavirus (HPV)," he says. "HPV-related tonsillar cancer can be considered sexually transmitted."

26 Amazing Facts About the Human Body

Mental Floss via YouTube
Mental Floss via YouTube

At some point in your life, you've probably wondered: What is belly button lint, anyway? The answer, according to Mental Floss editor-in-chief Erin McCarthy, is that it's "fibers that rub off of clothing over time." And hairy people are more prone to getting it for a very specific (and kind of gross-sounding) reason. A group of scientists who formed the Belly Button Biodiversity Project in 2011 have also discovered that there's a whole lot of bacteria going on in there.

In this week's all-new edition of The List Show, Erin is sharing 26 amazing facts about the human body, from your philtrum (the dent under your nose) to your feet. You can watch the full episode below.

For more episodes like this one, be sure to subscribe here.

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