Your anatomy


In this section, we’ll break down your anatomy in detail, and look at how your breasts and nipples change during pregnancy and when they start to make milk. 

Why is this relevant? To pump well, you need to learn more about your own body, specifically your breasts.

We’ll also look at why we need more research about varying breast and nipple sizes so that products (like pumps!) can be designed and better tailored to women. 

Here are the topics we're going to cover:

🍒 Your breast

🍒 Your areola and nipple

🍒 How your breast changes

❌ Common misconceptions about your anatomy

👩‍🔬 Why we need more research

Common questions


Your breast

Let’s start with the anatomy of a breast. 

☝️Anatomy of the breast showing the parts most involved in making milk.

On the surface, the visible part of the breast is the same for most people: the areola and the nipple. But for the female breast, the anatomy is different, all created through marvellous evolution so that we can produce milk and breastfeed.

So, let’s take a look inside your breast, because as you can imagine, it looks pretty different on the inside. 

Inside your breast

On the inside, your breast has a system for making milk that includes:

  1. Lobes. You have about 15 to 20 lobes or sections which are spaced out (not always evenly) around your breast like a clock. 
  2. Lobules. Inside each lobe, you have glandular tissue called lobules that look like a bunch of grapes. Each lobule gland has tiny sacs called alveoli that produce and hold milk.
  3. Milk ducts. Similar to the stem that holds grapes together, lobules are connected by terminal ducts that help transport the milk from your lobule out to your nipple through your milk ducts. 

Your lobes, lobules and milk ducts are sitting in fatty tissue, and held in place by connective fibrotic tissue. 

In amongst all of this are blood vessels which circulate your blood, lymph vessels which are part of your immune system and nerves. 

Read more on how milk gets made and pushed through your breast.

Your areola and nipple

Your areola

Areolas are typically round and darker than the rest of your breast. Areolae have their own set of glands called Montgomery glands, which secrete oil to help lubricate the nipple and skin to prevent chaffing while breastfeeding. 

These glands are also responsible for secreting a smell so that your baby can be guided to your nipple. This is how your baby can find its way toward your breast to feed just minutes after being born!

Why are they called Montgomery glands? After an Irish obstetrician who studied changes in the nipple over pregnancy, in the early 1800s. He got some things right, and some things less so.

Your nipple

Your nipple is the smaller section near the middle of your areola that typically sticks out when stimulated. There are approximately nine milk ducts in each of your nipples that are used to get the milk out of your breasts. Read more on how you make milk.

Size variation is the norm

Nipples and areolae can vary in shape, size and colour from person to person (and even from your left breast to your right!). This variation is totally normal. 

We know from our own surveys at Milkdrop that nipple diameter (measuring across from one side of the nipple to the other) alone can range from 5 mm to 40 mm. 

This is a big size difference, and just shows that there is no “perfect” nipple. 

Shape variation is the norm too

Nipples can also be long, round, flat or inverted, and anything in between. On top of this, your two nipples may be different from one another. Remember, they’re sisters, not twins. 

☝️This diagram shows some different types of nipples - all capable of pumping and nursing. 

We use four categories to describe nipple shape at Milkdrop: 

  • Inverted. A nipple that inverts (turns inward) when stimulated. Inverted nipples can extend out when pumping or nursing and stay there, or they can return to being inverted after). 
  • Flat. A nipple that everts (turns outwards) when stimulated, but is otherwise flat on the breast. 
  • Rounder. A nipple that projects out from the breast. 
  • Longer. A nipple that projects out farther from the breast. 

How your breast changes through pregnancy and lactation

Each trimester, your breast changes:

  • First trimester. Your system of milk ducts grows and branches out into your fatty tissue (thanks to more estrogen running through your body)
  • Second trimester. Your mammary glands are ready to produce milk, but they don’t yet, because you still have high estrogen and progesterone. You make colostrum instead. 
  • Third trimester. Once your estrogen and progesterone decrease (usually after your placenta is delivered), your milk production and letdowns start. 

Throughout the pregnancy, you will probably also notice your breasts getting larger, your areola and nipple getting darker, and your Montgomery Glands becoming more prominent.  

Not only do breasts typically get bigger, but your areolae and nipples also undergo other changes during pregnancy. The visible changes to your areola and nipple are caused by hormones and promote breastfeeding. 

The areola and nipples become visibly darker and larger during pregnancy for most people, which we think helps the baby see the contrast in colour between the areola and the rest of the breast. 

The Montgomery glands on the areola may also be more noticeable during pregnancy, although not always. In later pregnancy, you may even notice a sticky secretion from these glands, or perhaps you might see that water beads more when it’s on your breast. This is the secretion from the Montgomery glands as your breast prepares for lactation. 

As you well know, anything to do with the human body is complex. You can get into the weeds on breast changes during pregnancy and lactation in this article

Common misconceptions about your anatomy

Chances are you’ve never had to think much about the milk-making function of your breast, so there’s a lot to learn all at once. Here are some common misconceptions about the inner workings of your breast. 

Misconception #1

Your ducts are evenly spaced like a clock around the breast. 

You may have more ducts around some parts of your breast than another. This is why when you pump, you may get better flow in one part than another part. Also, it may explain why you may seem to experience blocked ducts in some parts of your breast, but not others. 

Misconception #2

You have 25-30 nipple ducts at your nipple where milk comes out. 

You probably have anywhere from 3 to 10 functional pores in your nipple where your milk comes out. Those other lumps in a ring around your areola are typically your Montgomery Glands which secrete amniotic fluid to lubricate your nipple, and also help your baby find your nipple after birth. It does seem like there’s still a bit of disagreement as to the average number of functional ducts, so maybe one to watch. 

Misconception #3

Your fat just sits behind your breast. 

Your fat is actually all mixed up with the glandular tissue in your breast. Some of that fat even comes out in your milk. 

Misconception #4

Your nipple and breast is similar to other breastfeeding mammals, like cows or goats. 

Those animals have lactiferous sinuses, which are storage cavities in the teat that hold milk. Humans don’t have this. Your milk goes straight from your alveoli (the little grape-like looking sac that creates and holds your milk) to your nipple.

Where do these misconceptions come from?

A few of these misconceptions come from the early 1800s (about the time of Netflix’s Bridgerton series if your history isn’t your strong suit), when breast anatomy was being studied through dissection by two men - Sir Astley Paston Cooper, 1st Baronet and William Fetherston Haugh Montgomery. Old-school, huh?

👆Sir Astley Paston Cooper

Apart from both having very long, rather fancy names, and both having a propensity for naming parts of the female breast after themselves - Montgomery Glands and Cooper’s Ligaments (which feels a little creepy in the modern day) - they both made advances and errors in what we know and assume about the breast. 

To be fair, they were injecting hot wax into milk ducts to try to define their shape, because they didn’t have ultrasounds to confirm their theories. That came 165 years later. 

Why it took over a century and a half (from 1840 to 2005) to really study the anatomy of the lactating breast, when we know breast milk to be critical in developing babies, we don’t know. 

👆Here is a drawing from one of Montgomery’s books, looking at nipple changes during pregnancy. 

And here’s a good (but long) book chapter on how our knowledge about the nipple has changed since the 1840s. 

Why we need more - and different - research

While there is a huge body of research on the anatomy of the nipple, it’s not quite in the way you might think. 

We know surprisingly and embarrassingly little about the various sizes and shapes of the female nipple, let alone the lactating nipple. 

While there was comprehensive study of lactating breasts in the 1840s, it wasn’t until 165 years later that researchers ultrasounded lactating breasts and showed that we had misunderstood quite a few things about how your breast and baby works to feed. Read this study, and this study for their learnings from the ultrasounds. 

🤔Did you know: this ultrasound research was funded by Medela (you know, the yellow breast pump brand) - it’s nice to see a long-term contribution to research like this from pump manufacturers. 

Why is lack of investment in research a problem? 

Because it means we aren’t providing women with the best information or with the best products. 

How can you design a product for women, like a breast pump, without understanding more about the lactating nipple? Read more about why women-centred design is important here (insert link).

Where is research funded when it comes to nipples?

There is some research, and there may be more done privately that we don’t know about, but it seems that most of the nipple-y research seems to focus on two areas. 

Plastic and reconstructive surgery

Much of this research is about how to create the “ideal” nipple for attractiveness. Surgeons need guidance on how and where to create and place the nipple for augmentation or reconstructive surgery, but still, surely the most “attractive” nipple is the one you have? 

Not so apparently. There are other characteristics typically determined by asking study participants to rank ‘attractiveness’ based on models or photographs of people’s breasts. These include breast width to upper buttock width ratio, nipple direction, breast width to shoulder width ratio and breast projection (i.e. sagginess). 

Some papers do talk about the patient’s own feeling of attractiveness, rather than someone else’s view of her attractiveness. It still feels odd to have created an environment where a woman feels her attractiveness is dependent on her nipple placement and shape, and then funded more research into defining that attractiveness better. 

Identifying nipples in images

Another investment area in understanding nipple shape is for developing algorithms that accurately and efficiently identify nipples within images. Ostensibly to identify pornography (fair enough), these algorithms are also behind defining ‘sensitive’ content on social media platforms, which often can simply be a …. lactating nipple. The silver lining of this area of research is that the same algorithms are also used in the software behind mammograms and other health technology. 

We are not intending to be rude to researchers, surgeons or people who are beneficially affected by the research and development we describe above. We would like to see a similar level of effort and funding to understanding the lactating nipple and supporting you to feed breast milk to your baby. 

Common questions on your anatomy

Have we not answered your question yet? 

Here are some common questions we hear on this topic.

I have small breasts, will I make enough milk? 

Some people assume if you have large breasts then you must produce a lot of milk and if you have small breasts then you may not produce enough. But the size of your breasts is no indication of your milk-making ability or volumes. 

What is the “ideal” breast and nipple for breastfeeding?

As you may have noticed, every breast and nipple is different and perfectly unique, but there is no “ideal” or “best” breast shape or nipple shape for breastfeeding or milk-production.

Some people assume if you have large breasts then you must produce a lot of milk and if you have small breasts then you may not produce enough. But the size of your breasts is no indication of your milk-making ability or volumes. 

There are some cases where your nipple shape or how it behaves (keep reading!), can mean that you need some extra help with nursing or pumping, especially in the early days. It certainly can be done though, so make sure you get help from a lactation consultant early if you think you’re having trouble. 

I have inverted nipples, can I still breastfeed? 

Yes! If you have inverted nipples (your nipples turn inwards when they’re stimulated), you might need a bit of help from a lactation consultant to get your nursing or pumping going. 

Although your nipple might be inverted at rest, you might notice that it everts (fancy word for turns outward) when you pump or nurse. It might stay there, or invert again afterward. 

Depending on how your baby is going, your lactation consultant might suggest you use a nipple shield to get started with nursing. 

In terms of pumping, there’s very little research to know if pumping is more painful or effective for people with inverted nipples. However, we do hear anecdotally from women who say that pumping is painful with inverted nipples because they need to stretch more to draw out milk. Take care when you pump to make sure you pump only at the highest comfortable level. 

How far will my nipple stretch when I breastfeed? 

Your nipple actually stretches when your baby draws your breast in to nurse, sometimes up to 2-3 times its normal length. If you’re pumping, it can be a shock to see your nipple stretch that far! 

Everybody’s tissue is different and stretches differently. You may notice that your nipple stretches to fill the flange tunnel completely and even touches the end. If this is the case, you may have ‘elastic nipples’. Unless you have pain, damage or find you have low milk flow, it’s not necessarily something you have to treat. Again, just watch for this, and call your lactation consultant if you think you need to. 

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Next up: learn about How you make milk