Curious about female breast anatomy

Dear Alice,

I just wanna know what the female breast is made of? Is milk really inside them? I'm just curious as to what gives them their size or shape. I would ask my mom but I'm afraid she'll get mad and won't tell me. I'm a 24-year-old guy and I'm just curious that's all. Thanks to anyone who can answer.

Dear Reader,

It’s completely natural to be curious about breasts — especially since almost everyone has them! Though breasts are commonly associated with people assigned female at birth, nearly every human — regardless of sex — has them, and they vary in size and shape. To answer your question — the components of breasts largely dictate their size and shape. Specifically, breast size is primarily affected by the presence of fibrous tissue and fat, while female breast shape is also affected by the presence of milk glands. Ready to no longer be a newbie on boobies? Keep on reading!

Regardless of sex assigned at birth, everyone’s breasts are largely made up of fatty tissue which lays on top of the pectoralis muscles (sometimes called pecs) and is protected by a layer of connective tissue called fascia. However, individuals assigned male at birth typically have less tissue, and fewer glands and ducts than individuals assigned female at birth. This is largely due to the capacity to become pregnant and produce milk, which in turn affects the shape and size of their breasts.

During and after pregnancy, there is a series of hormonal and physical changes which may impact the appearance of breasts. Typically between the fifth and sixth month of pregnancy and continuing after birth, the breasts of people assigned female at birth produce milk within small round glands called lobules. As the breasts become engorged with milk, their size appears bigger. Additionally, hormonal changes during pregnancy cause the areolas (dark areas around the nipples) to grow, and the overall breast size to increase. Though females who aren’t pregnant or haven’t recently breastfed still have these glands and ducts, they don’t experience as many changes to their breast size and shape.

Finally, it’s worth committing to “mammary” that breast shapes, sizes, and appearances vary widely from person to person. There may also be conditions where breasts have extra tissue (polymastia) or more than two nipples (polythelia). In rare cases, some people may have one or no breasts or nipples (amastia). With that said, you might want to check out Mayo Clinic’s slideshow on the typical female breast anatomy for a visual aid of all components described.

Hopefully this answered a few questions you “racked” up about breasts. Ta-ta!

Last updated Feb 16, 2018
Originally published Jan 23, 2015

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