11 Amazing Facts About the Nipple

The human body is an amazing thing. For each one of us, it's the most intimate object we know. And yet most of us don't know enough about it: its features, functions, quirks, and mysteries. Our series The Body explores human anatomy, part by part. Think of it as a mini digital encyclopedia with a dose of wow.

Despite its relatively small size on the human body, the nipple gets a lot of attention. Biologically, the nipple serves two key functions: In women, nipples deliver milk out of the ducts within the breast to babies, and for women and men, they serve as erogenous zones. Check out our list of fascinating facts about this often-misunderstood body part.


The nipple is the raised bump or protrusion on top of the breast that sits on the circular area known as the areola. The areola is often much larger in circumference than the actual nipple, as it holds small sweat glands called Montgomery glands (named for William Fetherstone Montgomery, an Irish obstetrician who first described them). The sole function of these glands is to secrete fluids during breastfeeding to lubricate the nipple and to produce a scent that attracts the baby to its mother's breast.


Not all nipples point jauntily outward. Men's and women's nipples can be inverted, essentially pointing inward. In the worst-case scenario, "the skin adheres to itself and has to peel open to [turn outward] initially, and [that] can be painful," Constance Chen, a board-certified plastic surgeon and clinical assistant professor of plastic surgery at Weill Cornell Medical College in New York, tells Mental Floss. For most women, however, an inverted nipple causes neither pain nor prevents breastfeeding with proper technique or nipple shields.


While most people have two nipples, one atop each breast (yes, both women and men have breasts), some people have extra or "supernumerary" nipples outside of the typical location. One Indian man was even found to have seven.

Leigh Anne O'Connor, a certified lactation consultant in New York, says these extra nipples can appear on or below an area named the Tail of Spence (after Scottish surgeon James Spence), which extends from the breast up into the armpit.

"Some people have nipples in their armpits, or even tiny breasts, and these nipples may leak," O'Connor tells Mental Floss. But an extra nipple is just an extra nipple—no cause for alarm or shame.


Since the main purpose of nipples is breastfeeding babies, and male breasts do not lactate, it begs the question: Why do men have nipples? Scientists Stephen Jay Gould and Richard C. Lewontin tried to get to the bottom of this conundrum in a seminal paper in 1993.

All human embryos start out essentially the same. If the embryo has XY chromosomes, a gene on the Y chromosome called SRY will activate within a couple weeks of conception and begin to differentiate the embryo into one with male genitals.

However, it turns out that breast tissue begins to develop before SRY kicks in, and since nipples in men essentially do no harm, Gould and Lewontin argue, there has simply never been a good enough reason—evolutionarily speaking—to do away with them. They linger because they're benign. Or as Andrew M. Simons, a professor of biology at Carleton University in Ottawa, Ontario wrote in Scientific American, "The presence of nipples in male mammals is a genetic architectural by-product of nipples in females. So, why do men have nipples? Because females do."


Who needs pecs when you have nipples like those of The Great Nippulini, a.k.a. Sage Werbock, a performer who makes a living demonstrating the mighty power of his nipples? Each nipple can lift 70 pounds, and he holds a Guinness record for the heaviest vehicle pulled by nipples for 20 meters (66 feet)—988.5 kilograms (2179.27 pounds). He has also lifted a variety of dumbbells, anvils, and bowling balls.


It's no secret that many people take sexual pleasure from nipple stimulation. However, Michael Reitano, an expert in sexual health and wellness at Roman Health in New York, brings up a study published in 2011 in which researchers set out to map the neurology of sexual stimulation in women. Through MRI imaging, they determined that "when [the nipple is] stimulated, the sensations travel to the same part of the brain that is stimulated when the clitoris, vagina, or cervix is stimulated," Reitano says. The study, published in the Journal of Sexual Medicine, also confirmed that it was possible for some women to have an orgasm by nipple stimulation alone.

While the same brain mapping has not yet been done on men, "there is every reason to believe that it has some capacity to function as a source of sexual pleasure for men as well," Reitano tells Mental Floss.


Nipples come in many colors, including pale pink, reddish-beige, brown, and black. Your own two nipples can even vary from each other, as can the areolae. "They also come in many different shapes," O'Connor says. "Some are more flat, while others can be quite bulbous. A person can have two nipples that look very different from each other. Asymmetry is normal."


While most forms of breast cancer affect the whole breast, Paget disease of the breast is a rare cancer that targets the skin and ducts of the nipple. "Most patients get a rash on the nipples that looks like a severe case of eczema. It is a cancer of breast epithelial (skin) cells," Chen says. Paget disease of the breast represents between 0.5 and 5 percent of all breast cancers.


In breast cancer cases where mastectomy—removal of the breast—is necessary, it is sometimes possible to spare the nipple, allowing for a more realistic post-treatment reconstruction, though sensation is often lost. However, Chen says that in certain cases, "it is possible to restore sensation to the nipples with nerve repairs and nerve grafts when a woman undergoes natural tissue breast reconstruction. Sensory restoration to the nipple after mastectomy is very cutting edge, but if you find the right surgeon, it is possible."


When a woman is ready to give birth but the baby isn't, one piece of often-shared advice is to stimulate the mother's nipples to induce labor. A 2005 analysis of six trial studies found a significant decrease in the number of women who hadn't gone into labor after 72 hours. Just under 63 percent of the women who received stimulation were not in labor versus 94 percent who hadn't received it.

The mechanism isn't entirely clear, but breast stimulation causes the uterus to contract. It may also help release the hormone oxytocin, which can start contractions. Once the baby's born, the baby's suckling also has benefits for the mother. "When a newborn suckles, the increased oxytocin causes the uterus to contract [and shrink to its original size over the subsequent weeks] following birth," Reitano explains.


If you've ever pumped your own breast milk or seen it done, you may have noticed that the milk doesn't just come out in a single stream. In a typical nipple, "There are between four and 20 outlets for the milk to come out—it can look like one stream or [coming from] various holes," O'Connor says.

10 Facts About Your Tonsils


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.

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