What Breasts Are Made Of

For all the fuss we, and society, make of women’s breasts, it’s insane how little many of us know about what they’re made of. Some people think they contain muscle and that working out will change their size or shape. (Spoiler alert: They don’t contain major muscles.)

We know they’re erogenous. We know they’re how we breastfeed. We know that breast cancer is something to be concerned about, too. But, breast anatomy is a mystery to many of us and we may still be confused what breasts are made of. Read on!

What Are Breasts Made Of

As we know, breasts come in all different shapes and sizes. But their makeup is actually similar no matter how your breasts appear from the outside. Let’s break down each component of breast anatomy.

Breast Anatomy 101

1. Fatty Tissue (Adipose Tissue) & Cooper’s Ligaments

Your breasts contain fatty tissue (also known as adipose tissue). This means your breast size can fluctuate with weight gain or loss. This tissue extends from the collarbone down to the underarm and across the chest wall to the middle of the ribcage.

Cooper’s ligaments are the fibrous connections between the inner side of the breast skin and the pectoral muscles. Cooper's ligaments are found under the skin of the breast, through and around the breast tissue.

2. Mammary Alveoli: Lobes & Lobules

Mammary alveoli are the site of milk production and storage in the mammary glandular tissue. Mammary alveoli cluster into groups called mammary lobes, which produce milk. Each breast has about 12 to 20 sections called lobes, each of which is composed of many smaller structures called lobules. 

Glandular Tissue

Lobules, sometimes referred to as your mammary glands, are a few millimeters long and hollow. In female breasts, lobules produce milk and store it.

Breast Tissue and Breast Cancer Risk

According to the National Breast Cancer Institute, it’s in the glandular tissue—lobes and lobules—that breast cancer is most likely to form. 

3. Milk Ducts or Lactiferous Ducts 

Wonder how your body produces milk and gets it from your lobules to the nipples? The lobules carry milk through the lactiferous ducts or “milk ducts” out of the nipples. Female breast anatomy includes approximately 15 to 20 milk ducts located in each breast.

4. Blood Vessels

Veins are a critical part of our bodily system, transporting blood to the heart. As you likely know, veins are more visible in certain parts of the body, especially the arms and legs. For some women, they are more visible in the breasts. 

Breast veins can also become more visible at certain times, including if/when you experience:

• Hormonal changes, including those caused by hormonal contraceptives
• Weight loss or gain
• Pregnancy
• Breast augmentation
• Age (skin becomes thinner with age)
• Certain health conditions, including mastitis, Mondor’s disease, and inflammatory breast cancer

5. Lymphatic Capillaries 

Lymphatic capillaries arise from the breast lobules.The lymph vessels lead to small bean-shaped organs called lymph nodes. These lymph nodes are found in clusters under the arm, above the collarbone, and in the chest. 

6. Areola 

That ring of pigmented skin around your nipples is called the areola. Like breasts themselves, the areola can differ in shape, size, and color for different women.

Fun fact: During pregnancy, the areola may become darker in color and grow in size. These changes are believed to help the newborn find the nipple and latch on to encourage nursing.

Your areola can also change size and shape if you gain or lose weight.

Montgomery Glands 

You might also notice that the areola has small, painless bumps. These are known as Montgomery glands. Montgomery glands are more prominent in some women than others, but we all have them. These glands secrete oil to help keep the skin lubricated.

In addition to Montgomery glands, all women have hair follicles on ​​the areolas. Some women have little fine hairs, which are almost invisible. However, other women may have more noticeable hairs. Again, this is considered normal.

7. Nipples

Finally, we’re all aware of our nipples! But that doesn’t mean they don’t also elicit their share of secrets and confusion. A lot of women wonder if their nipples are “normal.”

Rest assured, nipples come in as many sizes, shapes, and colors as breasts themselves. They can be large or small, pale or dark, different in shape (protruding, inverted, flat) and face upwards, downwards, sideways, any which way! 

Indeed, nipples can even differ from each other on the same woman. (It’s always important to remember that breasts are not identical to each other—think of them as sisters, not twins).

The majority of women have nipples that protrude a few millimeters from the areola in their normal state (they protrude more when you’re aroused). But inverted nipples are not uncommon, with an estimated 10–20% having at least one nipple that is inverted.

Nipples are, of course, where milk leaves a woman’s body during breastfeeding. But this isn’t the only purpose of nippes (or breasts!) They are, of course, an important erogenous zone. Nipple stimulation lights up the same parts of the brain as vaginal, clitoral, and cervix stimulation.

What Are Dense Breasts?

Now that we know what breasts are made of, you might wonder why some women’s breasts are referred to as “dense breasts.” This is a term you might hear when getting a mammogram. 

"Only a mammogram can show if a woman has dense breasts," according to the National Cancer Institute.

It's Common to Have Dense Breasts

Don’t panic if a mammography technologist says you have dense breasts. This simply refers to breast density: The amount of connective tissue a person has compared to fat. Fat is a low-density material and breast duct material is higher density. 

According to the Mayo Clinic: “Dense breast tissue refers to the appearance of breast tissue on a mammogram. It's a normal and common finding.

“Breast tissue is composed of milk glands, milk ducts, and supportive tissue (dense breast tissue), and fatty tissue (non-dense breast tissue). When viewed on a mammogram, women with dense breasts have more dense tissue than fatty tissue.”

Other diagnostic tools (such as breast ultrasound and breast magnetic resonance imaging, or MRI) can help detect breast cancer in women who have dense breast tissue, according to Johns Hopkins Medicine. 

Beneath the Breasts: Pectoral Muscle & Ribs

Many women believe working out can impact the shape of their breasts and reduce sagging. As we mentioned, there are no major muscles in the breasts, so this is a little bit of a fallacy.

However, the pectoral muscle passes underneath the breast and connects the chest and the arm. Exercises that target these muscles may help with posture and give you a little lift. To learn more about whether sagging breasts can be avoided (and what steps to take), click here.

Situated further below the pectoral muscle are your ribs.

When Your Breasts Change

Like all parts of your body, your breasts can undergo significant changes over the course of your lifetime. During puberty, when they begin to develop, one breast may grow faster than the other. You may also notice changes to the areola and nipples from the beginning of puberty to full development.

Within your monthly menstrual cycle, you may also notice changes to your breasts, including increased tenderness. 

And of course, there are significant changes over the course of pregnancy as your breasts prepare for nursing.

By the time menopause comes around, you may notice your breasts become smaller and the skin thins, resulting in a more sagging appearance.

While all of these changes are normal, it’s also worth familiarizing yourself with changes that might be less normal. Breast lumps and bumps should always be checked out by your healthcare provider. As well, excess, prolonged itching that does not respond to topical treatment should be reported.

Regular breast exams are an important healthcare step for all women and, when your doctor advises it necessary, you should also go for regular mammograms.

Beyond paying attention to your breast health, it’s also important to accept that breasts come in many shapes and sizes. Many women feel there’s something wrong with their breasts if they don’t conform to some beauty ideal. But really, this is an unrealistic standard that excludes the awesome variety and beauty that women exhibit.

Written by Jane Flanagan — Updated on March 1, 2022.

We hope you found this post informative — but remember: we’re not doctors and this post is not medical advice! While all posts are fact-checked and well researched, we always recommend you chat with your doctor about any questions or concerns you might have regarding a medical condition. We’re here to support and educate, but never with the aim of disregarding professional medical advice you’ve been given. Phew, now that that’s out of the way, you can go on living unapologetically free.