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7 Surprising Facts About the Chin

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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.

The humble chin, that bony protrusion at the bottom of your face, is a mysterious little body part that is a surprising source of controversy among researchers. Though popular culture derives great meaning out of how "strong" or "weak" chins are, very little science backs that up. Here, however, are seven actually scientific facts, which Mental Floss learned from experts, about the chin.

1. RESEARCHERS DISAGREE ABOUT THE PURPOSE OF A CHIN.

The most interesting thing about the chin, according to Faisal Tawwab, a family practice doctor with Multicare Physicians in Orlando, Florida, is that there is no precise answer as to why we even have one. "Prevailing theories include assistance with speech, to protect the jaw from chewing, as a way to measure attractiveness when seeking a partner, or a combination of all three," he tells Mental Floss. "Research to find the true purpose of the chin is ongoing. There are critiques around all of the current prevailing theories."

2. IT MIGHT HELP THE JAW STRESS LESS.

The chin may have evolved to protect the jaw from the unique stresses of shaping our mouths to form language, according to a 2007 study in the journal Medical Hypotheses. Your chin may help bear some of the muscle load of chewing and speaking (a valid reason to want a strong one).

3. THE CHIN IS CRITICAL TO CHEWING.

"The most important function of the chin is mastication [chewing] and lip continence," Francesco Gargano, a board certified plastic surgeon with The Plastic Surgery Center in New Jersey, tells Mental Floss. "Several muscles insert into the chin and are part of the occlusal plane," the space between your teeth when the mouth is closed. Research supports this theory, suggesting that the chin "helps buttress the jaw against certain mechanical stresses," including chewing, which produces a great deal of force.

4. CHINS MAY HAVE HELPED OUR ANCESTORS CHOOSE A MATE.

A more recent theory is that our chins helped us choose mates. "Males tend to have longer chins with a square appearance and flat base. Females tend to have narrower and rounder chins," says Gargano. A 2010 study in the American Journal of Physical Anthropology argues that there would be no difference in chin shape if it weren't related to sexual attraction because there's no functional difference; males and females ostensibly eat and talk the same way. Not everyone agrees. (See #7.)  

5. WE'RE THE ONLY ANIMALS WITH CHINS. 

While humans may share some things in common with animals, chins are not one of them. "Elephants are the only other creature with a body part similar to the chin," Tawwab says. But the elephant's "chin" is actually caused by a lack of lower teeth and a big lower lip. It's not a bony protrusion, which is a real chin—and a feature that's ours alone. The human chin is considered a cladistic apomorphy, Tawwab says: a feature or body part not found in the earliest forms of a clade (group of organisms sharing a common ancestor). In short, it's evidence of our species's evolution—and one of our defining physical characteristics.

6. DOES HAVING A CHIN CLEFT IMPROVE YOUR DATING PROSPECTS? 

"Historically, numerous cultures have assigned meanings to being born with a cleft chin, usually pertaining to luckiness in love," Tawwab says. The reality is much more mundane. "The current theory suggests that a cleft chin is actually caused by an incomplete fusion of the jaw bones before birth." There are several types of clefts, as well: vertical furrows, Y-shaped furrows, and round dimples. 

7. A CHIN MAY SIMPLY BE WHERE EVOLUTION STOPPED.

A chin may not have anything to do with withstanding pressure or attracting a mate, according to Nathan Holton, an anthropologist at the University of Iowa. His research suggests that the Homo genus (including humans, Neanderthals, and other relatives) simply evolved smaller faces—and Homo sapiens most of all. The lower jaw is the last part of the face to stop growing, which causes it to be more prominent as compared to other parts of the face. The prominent chin "is a secondary consequence of faces getting smaller," Holton writes.

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The Body
7 Essential Facts About the Pelvis
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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.

The pelvis, which crooner Elvis was famous for thrusting around in ways that raised eyebrows, is not actually a single body part but a term that refers to a collection of bones, muscles and organs below the waist. We spoke to Katherine Gillogley, department chair of obstetrics and gynecology with Mercy Medical Group in Sacramento, California, for these seven facts about the pelvis.

1. SO WHAT IS THE PELVIS, EXACTLY?

"The pelvis refers to the lower abdominal area in both men and women," Gillogley says. "An important function of the pelvis region is to protect organs used for digestion and reproduction, though all its functions are crucial," she says. It protects the bladder, both large and small intestines, and male and female reproductive organs. Another key role is to support the hip joints.

2. THE PELVIC BONES FORM A BASIN.

Four bones come together to form a bowl-like shape, or basin: the two hip bones, the sacrum (the triangle-shaped bone at the low back) and the coccyx (also known as the tailbone).

3. YOUR PELVIC FLOOR IS LIKE A TRAMPOLINE.

At the bottom of the pelvis lies your pelvic floor. You don't have to worry about sweeping it, but you might want to do Kegel exercises to keep it strong. The pelvic floor is like a "mini-trampoline made of firm muscle," according the Continence Foundation of Australia. Just like a trampoline, the pelvic floor is flexible and can move up and down. It also creates a surface (floor) for the pelvic organs to lie upon: the bladder, uterus, and bowels. It has holes, too, for vagina, urethra, and anus to pass through.

4. IT PLAYS A KEY PART IN WALKING.

Anyone who has ever broken a pelvic bone or pulled a pelvic muscle will know just how key a role the pelvis plays in such functions as walking and standing. "The pelvis also acts as a solid foundation for the attachment of the spinal column and legs," says Gillogley.

5. THE FEMALE PELVIS STARTS OUT LARGER, BUT NARROWS OVER TIME.

Gillogley says that the female pelvis "tends to be larger and wider" than the male, most likely to accommodate a baby during pregnancy and to make childbirth possible. However, women's pelvises narrow as they age, suggesting that they start out wider to accommodate childbearing and then shift when that is no longer necessary. A shifting pelvis shape is thought to be a key part of our evolutionary history, as it changed as when we began walking upright.    

6. PREGNANCY CHANGES THE PELVIS FOREVER.

During pregnancy the body secretes a hormone known as relaxin to help the body accommodate the growing baby and soften the cervix. However, what happens is, "the joints between the pelvic bones actually loosen and slightly separate during pregnancy and childbirth," Gillogley says. Sometimes, however, relaxin can make the joints too loose, causing a painful syndrome known as symphysis pubis dysfunction (SPD), causing the pelvic joint to become unstable, causing pain and weakness in the pelvis, perineum and even upper thighs during walking and other activities. Many women with the condition have to wear a pelvic belt. It usually resolves after pregnancy is over, though physical therapy may be necessary.

7. IT'S ACCIDENT PRONE.

According to the American Association for the Surgery of Trauma, about 8 to 9 percent of blunt trauma includes pelvic injury, Gillogley says. "These accidents include falls, motor vehicle crashes, bicycle accidents, and pedestrians being struck by moving vehicles. With these serious injuries, pelvic bones can fracture or dislocate and sometimes bladder injury even occurs." So take care with your pelvis—in worse-case scenarios, breaks of the pelvic bones can require pins, rods, and surgery to fix.

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The Body
10 Vital Facts About the Scrotum
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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.

The scrotum may appear to be nothing more than a bit of baggy skin, but it serves some very important functions for human health and reproduction. The testicles, which produce sperm, would be unprotected and subject to the elements without the scrotum—so without it, none of us might exist. To learn more, Mental Floss spoke to Brian Levine, a reproductive endocrinologist and fertility specialist at the New York office of the Colorado Center for Reproductive Medicine. 

1. THE SCROTUM HAS BUT ONE HUMBLE PURPOSE.

"The scrotum is a genius," Levine tells Mental Floss. While that may be a stretch, he says that the main purpose of the scrotum "is to hold the testicles outside of the body," which helps to keep the testicles cooler than body temperature. Because sperm are so sensitive to temperature fluctuations, this helps preserve their health.

2. HOT TESTICLES CAN CAUSE HEALTH AND FERTILITY PROBLEMS.

"Increased body temperature or temperature in general [such as a hot tub] leads to chromosomal abnormalities. By keeping the temperature lower you protect the DNA being formed to put the sperm together from having inborn errors," Levine explains.

3. TEMPERATURE REGULATES TESTICLE HEIGHT.

As the body gets colder, muscle fibers bring the scrotum closer to the body to regulate them. When the person is warmer, they will hang lower from the body. "The average person has one testicle higher than the other," Levine says. Size and shape variance of testicles is not in and of itself cause for concern—unless you experience a sudden change.

4. COOLER SPERM ALSO SWIM BETTER …

Also by keeping the testicles at a lower temperature, metabolically, Levine says, "you keep sperm swimming slower, so you end up preserving them."

5. … WHICH IS WHY SOME HAVE SUGGESTED EXPOSING THE SCROTUM TO OPEN FLAME OR A HOT-WATER SOAK.

A 2013 study [PDF] on birth control methods of an indigenous culture in Zimbabwe describes how men were instructed to expose their testicles to "above average heat from fire" in the belief that this would weaken the sperm. While there is a connection between temperature and sperm health, this is not a recommended practice for birth control as it is unlikely to successfully reduce the sperm count. In addition, the study notes, "testicles with too high of a body temperature are associated with testicular cancers," though others argue that the jury is still out on that purported connection. Either way, you should probably keep your scrotum away from open flame.

In a similar vein, Marthe Voegeli, a Swiss doctor and early pioneer in fertility in the 1950s, designed a study in which men sat in a shallow or testes-only bath of 116°F for 45 minutes daily for three weeks. Her study claimed that this resulted in between four and six months of infertility. Fertility returned to normal eventually, and children born of those men were healthy and normal. She took her method to India, to help families suffering from famine and poverty prevent further pregnancies. While she claimed her methods to be successful, most doctors today would not recommend this as a reliable contraceptive practice.

6. YOU CAN GET MELANOMA OF THE SCROTUM.

Even the scrotum is susceptible to cancer, Levine points out. "Wherever there's skin, you can get melanoma," he says. This can be a result of metastases of cancer that spread from somewhere else in the body, or, if you're a nude sunbather, be warned: "If you expose it to sunlight, you can get melanoma."

7. LACK OF A SCROTUM CAN MEAN THIS …

If you are male, not prepubescent, and don't have a scrotum, it may mean you have undescended testicles, Levine says, "which can end up leading to infertility." Most testicles will descend eventually, but sometimes they can be helped along by surgery.

8. BE AWARE OF THESE COMMON CONDITIONS OF THE SCROTUM.

Common issues of the scrotum that may require surgical intervention include varicoceles, which are essentially varicose veins in the scrotum that can cause infertility by pooling blood, which can effect sperm count and motility. Varicoceles can also cause testicles to fail to develop normally or shrink. A hydrocele, which doctors informally call "water on the testicle," Levine says, is simply a fluid-filled cyst that surrounds a testicle and causes swelling in the scrotum. Levine adds that since the scrotum allows for good evaluation of testicles, "If you feel any lumps, bumps or abnormalities, you should see a medical professional."

9. SURGICAL TECHNIQUES FOR THE SCROTUM AND TESTICLES HAVE COME A LONG WAY.

Should you need surgery for one of those conditions, or for a vasectomy, Levine reassures that modern day surgical techniques "mostly spare the scrotum and require a minimal, barely visible incision in the testicle." Weill Cornell Medical Center has even perfected what they call a no-scalpel vasectomy that uses specialized forceps instead.

10. WHY WERE CHIMNEY SWEEPS PRONE TO SCROTAL CANCER?

In the late 1700s and early 1800s, chimney sweeps—who were often young boys because they were small enough to fit—would develop scrotal cancer from creosote collecting between the skin folds on the scrotum.

Sir Percival Pott, an English surgeon considered the father of orthopedics and the first to draw the connection between occupations and certain illnesses, also made the connection between chimney sweeps and scrotal cancer, writing: " … there is a different disease peculiar to a certain set of people, which has not, at least to my knowledge, been publicly noticed; I mean the chimney-sweeper's cancer. It is a disease which makes its first attack on, and appearance in, the inferior part of the scrotum; where it produces a superficial, painful, ragged, ill-looking sore, with hard and rising edges: the trade call it the soot-wart." (We know now that a chemical in soot caused genetic damage to chromosome 17.)

After this connection was made, physicians recommended that chimney sweeps change their clothes weekly and wash their genitals daily.   

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