This is a bit complicated so bear with me.
When someone gets pregnant, at a certain point they’ll be able to produce milk. Nipples are usually closed off until this happens right? How does the nipple open up to allow milk through? Does the hole close up eventually or is it just permanently open with no milk to go through? Why isn’t the nipple open all the time?
In: Biology
Biologically milk glands are a lot like sweat glands. When a woman gives birth—specifically, when a pregnancy of adequate duration ends*—the resulting hormonal changes trigger the glands to produce milk. At first, the quantity is small, but the glands produce based on how much is expressed. Take the milk out, the glands produce more. Thus, as a baby grows, the mother’s milk supply increases to accommodate the bigger appetite. Over time, the quality of the milk changes in response to chemical/hormonal triggers from the baby’s saliva.
The way milk is expressed is called “the let-down.” There is always some residual milk in the ducts, but stimulation from a pump or the nursing action of a baby’s mouth triggers a rapid increase in production. For me, that felt a little like a sneeze or an orgasm in that it was a feeling that built and then released. (Breastfeeding was not sexual, but it felt like the same kind of stimulation-release process, to be clear.) Once the baby has drunk from both sides, the feeding is over. And mom guzzles a big glass of water to replenish.
*it doesn’t matter how the baby is born, or even whether it is born alive. I’m not sure how early in pregnancy the process is primed—certainly by 19-20 weeks. When the pregnancy ends, the milk production process will begin. If the milk isn’t expressed, production will taper off and stop, but that process can be very painful.
I feel like you are imagining nipples as having a little door that opens. Like a cap pops off or something. They just have a bunch of pores. You can look at your own nipples and see that. You can see it even if you are a boy!
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