7 Surprising Facts About the Breast

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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. Of all the organs of the body, the humble breast has come to represent so much more than its essential functions. American culture places undue value on size, shape, and appearance of breasts, which can make it easy to forget the essential function of the breast, from an evolutionary standpoint, which is primarily for feeding our offspring. Mental Floss spoke to a pair of specialists about the breasts. Here are seven things we learned.

1. BREASTS ARE GLANDS.

Beneath the fleshy mound that we think of as a breast is the less glamorously named mammary gland, a complex network of fat cells and tubes that are capable of producing milk for babies. If a woman becomes pregnant, the milk ducts, sac-like structures, fill first with colostrum before the baby is born and then breast milk after, and send it via little channels called lobules to the nipple, where the milk exits.

2. BREASTS ARE SISTERS, NOT TWINS.

According to Constance Chen, a plastic and reconstructive surgeon and director of microsurgery at New York Eye & Ear Infirmary of Mount Sinai Hospital, two breasts are rarely, if ever, identical. "Breasts come in all shapes and sizes," she tells Mental Floss. "There are lots of different ways to be normal." The same is also true for nipples and their areolae, the darker colored skin around the nipples.

3. INVERTED NIPPLES ARE NORMAL.

An inverted nipple is a normal occurrence "caused by adhesions at the base of the nipple that bind the skin to the underlying tissue," according to a team of specialists at Columbia University that answers medical questions in a column called "Go Ask Alice." It's possible to have one inverted nipple and not the other, or both. In general, it should cause very little discomfort or problems, with the exception of breastfeeding. Sometimes an inverted nipple can be difficult for an infant to latch onto, but there are methods to help the nipple protrude again, such as nipple shields. In very rare cases, a nipple that becomes inverted may be a sign of breast cancer, in which a tumor is pulling on the tissue and causes it to invert.

4. SMOKING CAN CAUSE BREASTS TO DROOP, BUT BREASTFEEDING DOESN'T.

Many women blame breastfeeding for breast droop, but the facts don't bear that out. While pregnancy can change the elasticity of ligaments in the breasts, breastfeeding merely changes the size of the breasts, but has little impact on the elasticity of the skin. Smoking, on the other hand, is a direct antagonist to elastin, the substance that makes all skin supple, which can lead to drooping breasts.

5. BREAST CANCER DOES NOT DISCRIMINATE.

People often believe that the only way they're likely to get breast cancer is if they have a family history. According to Chen, this is not accurate: "Most people who get breast cancer have no family history," she notes. Beyond genetics, risk factors include "getting older, benign breast problems, more exposure to estrogen, drinking alcohol, and exposure to radiation." And men can get breast cancer, too. "It makes up less than 1 percent of all cancers in men, but it's not a part to be ignored," Jay Harness, a breast cancer and reconstructive surgeon at St. Joseph Hospital in Orange, California, tells Mental Floss. Women and men should both seek preventative cancer screenings, especially if there is a family history of the aggressive BRCA1 gene that carries a significant risk of cancer in men and women. Early detection is key to helping treat breast cancer.

6. MIDWIVES OF OLD READ BREASTS LIKE BOOKS.

According to a class at Stanford titled "A History of the Body," early midwives and medical practitioners made meaning of the colors of women's breasts. A 17th-century midwife, Jane Sharp, wrote about the English women she tended to: "The Nipples are red after Copulation, red as a Strawberry, and that is their Natural colour: But Nurses Nipples, when they give Suck, are blue, and they grow black when they are old."

7. IT'S NOT JUST MEN WHO STARE AT WOMEN'S BREASTS.

Psychologists from the University of Nebraska-Lincoln did a study in 2013 to determine whether men were alone in their alleged fascination with women's breasts. For the study, titled "My Eyes Are Up Here: The Nature of the Objectifying Gaze Toward Women," 29 women and 36 men were fitted up with eye-tracking technology and shown women with "body shapes that fit cultural ideals of feminine attractiveness to varying degrees." They were told to focus on the appearance versus the personality of the women. Both male and female participants spent more time looking at the women's breasts than they did their faces, especially if a woman had a "high ideal" body shape: hourglass, with a small waist and large breasts.

Why Can You Sometimes See Your Breath?

Chalabala/iStock via Getty Images
Chalabala/iStock via Getty Images

The human body is made up of about 60 percent water, meaning that when we breathe, we don’t just exhale carbon dioxide—we also exhale a certain amount of water vapor.

Water molecules need a lot of energy in order to remain in a gaseous form. When the warm water vapor molecules from your lungs reach colder air, they condense into “tiny droplets of liquid water and ice,” according to Wonderopolis. In fact, this process of condensation is also how clouds are formed.

But it’s actually relative humidity, not just temperature, that determines whether you can see your breath. The water vapor in your breath condenses into a liquid when it hits dew point—the temperature at which the air is saturated and can’t hold any more water in gas form. Since cold air can’t hold as much water vapor as warm air, you're much more likely to see your breath on a chilly day, but that's not always the case.

On more humid days, you may be able to see your breath even when it’s relatively warm outside. That’s because the air is already more saturated, making the dew point higher. And on especially dry days, even if it's cold outside, you may not be able to see your breath at all. Dry, unsaturated air can hold more water vapor, so you can huff and puff without seeing any evidence of it at all.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

7 Facts About Blood

Moussa81/iStock via Getty Images
Moussa81/iStock via Getty Images

Everyone knows that when you get cut, you bleed—a result of the constant movement of blood through our bodies. But do you know all of the functions the circulatory system actually performs? Here are some surprising facts about human blood—and a few cringe-worthy theories that preceded the modern scientific understanding of this vital fluid.

1. Doctors still use bloodletting and leeches to treat diseases.

Ancient peoples knew the circulatory system was important to overall health. That may be one reason for bloodletting, the practice of cutting people to “cure” everything from cancer to infections to mental illness. For the better part of two millennia, it persisted as one of the most common medical procedures.

Hippocrates believed that illness was caused by an imbalance of four “humors”—blood, phlegm, black bile, and yellow bile. For centuries, doctors believed balance could be restored by removing excess blood, often by bloodletting or leeches. It didn’t always go so well. George Washington, for example, died soon after his physician treated a sore throat with bloodletting and a series of other agonizing procedures.

By the mid-19th century, bloodletting was on its way out, but it hasn’t completely disappeared. Bloodletting is an effective treatment for some rare conditions like hemochromatosis, a hereditary condition causing your body to absorb too much iron.

Leeches have also made a comeback in medicine. We now know that leech saliva contains substances with anti-inflammatory, antibiotic, and anesthetic properties. It also contains hirudin, an enzyme that prevents clotting. It lets more oxygenated blood into the wound, reducing swelling and helping to rebuild tiny blood vessels so that it can heal faster. That’s why leeches are still sometimes used in treating certain circulatory diseases, arthritis, and skin grafting, and helps reattach fingers and toes. (Contrary to popular belief, even the blood-sucking variety of leech is not all that interested in human blood.)

2. Scientists didn't understand how blood circulation worked until the 17th century.

William Harvey, an English physician, is generally credited with discovering and demonstrating the mechanics of circulation, though his work developed out of the cumulative body of research on the subject over centuries.

The prevailing theory in Harvey’s time was that the lungs, not the heart, moved blood through the body. In part by dissecting living animals and studying their still-beating hearts, Harvey was able to describe how the heart pumped blood through the body and how blood returned to the heart. He also showed how valves in veins helped control the flow of blood through the body. Harvey was ridiculed by many of his contemporaries, but his theories were ultimately vindicated.

3. Blood types were discovered in the early 20th century.

Austrian physician Karl Landsteiner discovered different blood groups in 1901, after he noticed that blood mixed from people with different types would clot. His subsequent research classified types A, B and O. (Later research identified an additional type, AB). Blood types are differentiated by the kinds of antigens—molecules that provoke an immune system reaction—that attach to red blood cells.

People with Type A blood have only A antigens attached to their red cells but have B antigens in their plasma. In those with Type B blood, the location of the antigens is reversed. Type O blood has neither A nor B antigens on red cells, but both are present in the plasma. And finally, Type AB has both A and B antigens on red cells but neither in plasma. But wait, there’s more! When a third antigen, called the Rh factor, is present, the blood type is classified as positive. When Rh factor is absent, the blood type is negative.

Scientists still don’t understand why humans have different blood types, but knowing yours is important: Some people have life-threatening reactions if they receive a blood type during a transfusion that doesn’t “mix” with their own. Before researchers developed reliable ways to detect blood types, that tended to turn out badly for people receiving an incompatible human (or animal!) blood transfusion.

4. Blood makes up about 8 percent of our total body weight.

Adult bodies contain about 5 liters (5.3 quarts) of blood. An exception is pregnant women, whose bodies can produce about 50 percent more blood to nourish a fetus.)

Plasma, the liquid portion of blood, accounts for about 3 liters. It carries red and white blood cells and platelets, which deliver oxygen to our cells, fight disease, and repair damaged vessels. These cells are joined by electrolytes, antibodies, vitamins, proteins, and other nutrients required to maintain all the other cells in the body.

5. A healthy red blood cell lasts for roughly 120 days.

Red blood cells contain an important protein called hemoglobin that delivers oxygen to all the other cells in our bodies. It also carries carbon dioxide from those cells back to the lungs.

Red blood cells are produced in bone marrow, but not everyone produces healthy ones. People with sickle cell anemia, a hereditary condition, develop malformed red blood cells that get stuck in blood vessels. These blood cells last about 10 to 20 days, which leads to a chronic shortage of red blood cells, often causing to pain, infection, and organ damage.

6. Blood might play a role in treating Alzheimer's disease.

In 2014, research led by Stanford University scientists found that injecting the plasma of young mice into older mice improved memory and learning. Their findings follow years of experiments in which scientists surgically joined the circulatory systems of old and young mice to test whether young blood could reverse signs of aging. Those results showed rejuvenating effects of a particular blood protein on the organs of older mice.

The Stanford team’s findings that young blood had positive effects on mouse memory and learning sparked intense interest in whether it could eventually lead to new treatments for Alzheimer’s disease and other age-related conditions.

7. The sight of blood can make people faint.

For 3 to 4 percent of people, squeamishness associated with blood, injury, or invasive medical procedures like injections rises to the level of a true phobia called blood injury injection phobia (BII). And most sufferers share a common reaction: fainting.

Most phobias cause an increase in heart rate and blood pressure, and often muscle tension, shakes, and sweating: part of the body’s sympathetic nervous system’s “fight or flight” response. But sufferers of BII experience an added symptom. After initially increasing, their blood pressure and heart rate will abruptly drop.

This reaction is caused by the vagus nerve, which works to keep a steady heart rate, among other things. But the vagus nerve sometimes overdoes it, pushing blood pressure and heart rate too low. (You may have experienced this phenomenon if you’ve ever felt faint while hungry, dehydrated, startled, or standing up too fast.) For people with BII, the vasovagal response can happen at the mere sight or suggestion of blood, needles, or bodily injury, making even a routine medical or dental checkup cause for dread and embarrassment.

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