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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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Medicine
This Soft Artificial Heart May One Day Shorten the Heart Transplant List
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ETH Zurich

If the heart in the Functional Materials Laboratory at ETH Zurich University were in a patient in an operating room, its vital signs would not be good. In fact, it would be in heart failure. Thankfully, it's not in a patient—and it's not even real. This heart is made of silicone.

Suspended in a metal frame and connected by tubes to trays of water standing in for blood, the silicone heart pumps water at a beat per second—a serious athlete's resting heart rate—in an approximation of the circulatory system. One valve is leaking, dripping onto the grate below, and the water bins are jerry-rigged with duct tape. If left to finish out its life to the final heartbeat, it would last for about 3000 beats before it ruptured. That's about 30 minutes—not long enough to finish an episode of Grey's Anatomy

Nicolas Cohrs, a bioengineering Ph.D. student from the university, admits that the artificial heart is usually in better shape. The one he holds in his hands—identical to the first—feels like taut but pliable muscle, and is intact and dry. He'd hoped to demonstrate a new and improved version of the heart, but that one is temporarily lost, likely hiding in a box somewhere at the airport in Tallinn, Estonia, where the researchers recently attended a symposium.

Taking place over the past three years, the experimental research is a part of Zurich Heart, a project involving 17 researchers from multiple institutions, including ETH, the University of Zurich, University Hospital of Zurich, and the German Heart Institute in Berlin, which has the largest artificial heart program in Europe.

A BRIDGE TO TRANSPLANT—OR TO DEATH

Heart failure occurs when the heart cannot pump enough blood and oxygen to support the organs; common causes are coronary heart disease, high blood pressure, and diabetes. It's a global pandemic, threatening 26 million people worldwide every year. More than a quarter of them are in the U.S. alone, and the numbers are rising.

It's a life-threatening disease, but depending on the severity of the condition at the time of diagnosis, it's not necessarily an immediate death sentence. About half of the people in the U.S. diagnosed with the disease die within five years. Right now in the U.S., there are nearly 4000 people on the national heart transplant list, but they're a select few; it's estimated that upwards of 100,000 people need a new heart. Worldwide, demand for a new heart greatly outpaces supply, and many people die waiting for one.

That's why Cohrs, co-researcher Anastasios Petrou, and their colleagues are attempting to create an artificial heart modeled after each patient's own heart that would, ideally, last for the rest of a person's life.

Mechanical assistance devices for failing hearts exist, but they have serious limitations. Doctors treating heart failure have two options: a pump placed next to the heart, generally on the left side, that pumps the blood for the heart (what's known as a left ventricular assist device, or LVAD), or a total artificial heart (TAH). There have been a few total artificial hearts over the years, and at least four others are in development right now in Europe and the U.S. But only one currently has FDA approval and CE marking (allowing its use in European Union countries): the SynCardia total artificial heart. It debuted in the early '90s, and since has been implanted in nearly 1600 people worldwide.

While all implants come with side effects, especially when the immune system grows hostile toward a foreign object in the body, a common problem with existing total artificial hearts is that they're composed of hard materials, which can cause blood to clot. Such clots can lead to thrombosis and strokes, so anyone with an artificial heart has to take anticoagulants. In fact, Cohrs tells Mental Floss, patients with some sort of artificial heart implant—either a LVAD or a TAH—die more frequently from a stroke or an infection than they do from the heart condition that led to the implant. Neurological damage and equipment breakdown are risky side effects as well.

These complications mean that total artificial hearts are "bridges"—either to a new heart, or to death. They're designed to extend the life of a critically ill patient long enough to get on (or to the top of) the heart transplant list, or, if they're not a candidate for transplant, to make the last few years of a person's life more functional. A Turkish patient currently holds the record for the longest time living with a SynCardia artificial heart: The implant has been in his chest for five years. Most TAH patients live at least one year, but survival rates drop off after that.

The ETH team set out to make an artificial heart that would be not a bridge, but a true replacement. "When we heard about these problems, we thought about how we can make an artificial heart that doesn't have side effects," he recalls.

USING AN ANCIENT TECHNIQUE TO MAKE A MODERN MARVEL

Using common computer assisted design (CAD) software, they designed an ersatz organ composed of soft material that hews closely to the composition, form, and function of the human heart. "Our working hypothesis is that when you have such a device which mimics the human heart in function and form, you will have less side effects," Cohrs says.

To create a heart, "we take a CT scan of a patient, then put it into a computer file and design the artificial heart around it in close resemblance to the patient's heart, so it always fits inside [the body]," Cohrs says.

But though it's modeled on a patient's heart and looks eerily like one, it's not identical to the real organ. For one thing, it can't move on its own, so the team had to make some modifications. They omitted the upper chambers, called atria, which collect and store blood, but included the lower chambers, called ventricles, which pump blood. In a real heart, the left and right sides are separated by the septum. Here, the team replaced the septum with an expansion chamber that is inflated and deflated with pressurized air. This action mimics heart muscle contractions that push blood from the heart.

The next step was to 3D-print a negative mold of the heart in ABS, a thermoplastic commonly used in 3D printing. It takes about 40 hours on the older-model 3D printers they have in the lab. They then filled this mold with the "heart" material—initially silicone—and let it cure for 36 hours, first at room temperature and then in an oven kept at a low temperature (about 150°F). The next day, they bathed it in a solvent of acetone, which dissolved the mold but left the printed heart alone. This process is essentially lost-wax casting, a technique used virtually unchanged for the past 4000 years to make metal objects, especially bronze. It takes about four days.

The resulting soft heart weighs about 13 ounces—about one-third more than an average adult heart (about 10 ounces). If implanted in a body, it would be sutured to the valves, arteries, and veins that bring blood through the body. Like existing ventricular assist devices and total artificial hearts on the market, it would be powered by a portable pneumatic driver worn externally by the patient.

FROM 3000 TO 1 MILLION HEARTBEATS

In April 2016, they did a feasibility test to see if their silicone organ could pump blood like a real heart. First they incorporated state-of-the-art artificial valves used every day in heart surgeries around the world. These would direct the flow of blood. Then, collaborating with a team of mechanical engineers from ETH, they placed the heart in a hybrid mock circulation machine, which measures and simulates the human cardiovascular system. "You can really measure the relevant data without having to put your heart into an animal," says Cohrs.

Here's what the test looked like.

"Our results were very nice," Cohrs says. "When you look at the pressure waveform in the aorta, it really looked like the pressure waveform from the human heart, so that blood flow is very comparable to the blood flow from a real human heart."

Their results were published earlier this year in the journal Artificial Organs.

But less promising was the number of heartbeats the heart lasted before rupturing under stress. (On repeated tests, the heart always ruptured in the same place: a weak point between the expansion chamber and the left ventricle where the membrane was apparently too thin.) With the average human heart beating 2.5 billion times in a lifetime, 3000 heartbeats wouldn't get a patient far.

But they're making progress. Since then, they've switched the heart material from silicone to a high-tech polymer. The latest version of the heart—one of which was stuck in that box in the Tallinn airport—lasts for 1 million heartbeats. That's an exponential increase from 3000—but it's still only about 10 days' worth of life.

Right now, the heart costs around $400 USD to produce, "but when you want to do it under conditions where you can manufacture a device where it can be implanted into a body, it will be much more expensive," Cohrs says.

The researchers know they're far from having produced an implantable TAH; this soft heart represents a new concept for future artificial heart development that could one day lead to transplant centers using widely available, easy-to-use design software and commercially available 3D-printers to create a personalized heart for each patient. This kind of artificial heart would be not a bridge to transplantation or, in a few short years, death, but one that would take a person through many years of life.

"My personal goal is to have an artificial heart where you don't have side effects and you don't have any heart problems anymore, so it would last pretty much forever," Cohrs says. Well, perhaps not forever: "An artificial heart valve last 15 years at the moment. Maybe something like that."

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The Body
9 Interesting Facts About the Ribs
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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.

Ribs are not just an incredibly tasty order on the menu at the nearest steak house: These bony spindles in your torso attach to your sternum (breast bone) to protect your lungs, heart, spleen, and most of the liver and help with giving shape to your chest cavity, which assists in breathing. Ribs are protective on the one hand, but if badly broken, your ribs can turn lethal to you, piercing your organs. Mental Floss spoke to John Martinez, MD, an urgent care provider with Dignity Health Medical Foundation in California for these nine fascinating facts about the ribs.

1. YOUR RIBS MOVE LIKE A BUCKET HANDLE.

The ribs allow chest expansion for breathing, Martinez explains. "They function similarly to the bucket handle on a bucket and swing upwards as we take a breath, allowing the thoracic cavity to expand." This increase in the thoracic cavity makes it easier to take a breath.

2. YOU HAVE THREE TYPES OF RIBS.

The human skeleton has 12 pairs of ribs. Working from the top of the torso down, ribs 1 to 7 are considered "true ribs," as they connect directly from the spine to the sternum, Martinez says. Ribs 8 to 10 are called "false ribs" because they don't connect directly, but have cartilage that attaches them to the sternum. Ribs 11 and 12 are called "floating ribs" because they only connect to the spine in back. These, he says, "are much shorter."

3. THIS MYTH ABOUT WOMEN'S RIBS PERSISTS.

In an effort to prove the Bible story of Eve as wrought from Adam's rib "true," pastors and Sunday School teachers sometimes pass along a tale that women have more ribs than men. It's not true (and that story is sexist, anyway). Gender plays no part in the number of ribs you have: It's 12 ribs for everyone. However, women's ribs are about 10 percent smaller in volume on average than men's ribs.

4. IN RARE INSTANCES, HUMANS CAN HAVE A "GORILLA RIB."

In rare cases, which have nothing to do with gender, a human might turn up sporting extra lumbar ribs, for a total of 13 pairs of ribs, much like our distant cousins, the gorillas. Thus, it's colloquially known as a "gorilla rib."

5. RIBS ARE THE REASON NEANDERTHALS DIDN'T NEED BELTS.

Neanderthals had wider, thicker rib cages than we modern slim-waisted humans, which would have made them terrible models for skinny jeans. A 2016 study in American Journal of Physical Anthropology found that the Ice-Age diet is likely responsible for the larger ribcage and wider pelvis in Neanderthals. Essentially, carbs were scarce and fat was abundant. This led to an enlarged liver, kidneys and "their corresponding morphological manifestations," the authors write. In other words, they needed more space to house bigger organs.

6. TWO VERY DIFFERENT KINDS OF ATHLETE SHARE ONE COMMON INJURY. 

"Rowers and baseball pitchers are the most common athletes to suffer from stress fractures of the ribs," Martinez says. This is caused by the serratus anterior muscle pulling on the delicate ribs. "Other athletes that may be more likely to suffer from rib stress fractures include golfers, dancers, weightlifters and volleyball players," he adds.

7. YOU CAN SNEEZE YOUR WAY TO A RIB FRACTURE.

"True" rib fractures—where the bone breaks all the way through—are usually from traumatic events such as "a hard football tackle [or] car accident," Martinez says. However, sometimes a rib fracture can occur "from sneezing or coughing due to the force of the contracting chest wall muscles on the ribs." Treatment for true rib fractures is the same as rib stress fractures.

8. WAIST TRAINING USED TO BE ALL THE RAGE … AND STILL SOMETIMES IS.

Women have historically worn corsets, undergarments that cinch the torso in, particularly at the waist, bringing ribs and organs closer together for a smaller waist and more prominent bust. Despite corsets having gone out of fashion by the 1920s, when women began to prefer the looser, more flowing garments of the Flapper era, a number of contemporary women still wear them for reasons ranging from aesthetics to performance art, spawning a practice known as tight lacing or waist training. In this movement, women actively whittle their waists down to exceptionally small circumferences.

Doctors warn that there is risk of permanent damage to squished organs, as well as such uncomfortable syndromes as acid reflux syndrome and back pain. But it doesn't stop those who love the look.

9. THE GUINNESS RECORD HOLDER FOR A TINY WAIST IS 15 INCHES.

2011 Guinness Book of World Records winner Cathie Jung got her waist down to 15 inches through tight lacing by wearing corsets 24 hours a day, and moving down to smaller and smaller sizes. Her waist now has the same circumference as a regular jar of mayonnaise.

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