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Breast Anatomy

In my breastfeeding journey I found a basic understanding of anatomy was invaluable to my understanding of how breastfeeding works. Here's a quick diagram (made by yours truly) & explanation of the key milk-making parts of your lovely lady lumps.

Milk is produced in the alveoli. Terminology gets tricky but basically: alveoli group into lobules, lobules into lobes & collectively these are the ‘Mammary Glands’.


Hormones (prolactin, growth hormones & insulin) cause your alveoli to take nutrients from your blood supply and turn them into breast milk.


Physical stimulation of your nipple (via your baby sucking) cues your brain to produce oxytocin, which triggers the cells around your alveoli to contract & squeeze (or "let-down") milk through your ducts & out your nipple for your baby to drink.


This transporting of the milk from the alveoli down through the ducts is called the “let-down” reflex. While it feels different for everyone, it can be quite strong & sometimes uncomfortable.


The letdown is often described as a tingling, a feeling of sudden fullness or stinging & can take up to 2min to get going. But does that mean that there is no milk until you ‘let-down’? No.


Your breasts always have milk in them, even if they don’t feel full. Your lobules & sinuses (near the base of your nipple) make sure to store milk so that your baby doesn’t have to wait two minutes for a feed (a lifetime for a newborn!), particularly if it’s been a while since their last drink. This is especially important considering that sucking at the breast is exhausting for brand new bubs, & often why they have a big sleep after each feed.


Think of it like this: your baby sucks at your nipple, which causes your brain to go "ok, milk time, let's turn the taps on", this is what the letdown is. While your bub is waiting, your stored milk trickles out, your letdown reflex happens & then the flow really gets going. All making for a happy and full baby!


Did you breastfeed your bub? What did you learn & what did you wish you knew before you started?


References: Greenfield et al 2001; Geddes 2007; Woolridge 1986

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