7 Surprising Facts About the Breast

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.