Where Is Your Sternum?
Thanks to WordPress, I get to see some of the search terms that bring people here. A surprising number indicate that people are stumbling into my corner of the Internet on their mighty search for… where exactly the sternum is located.
This absolutely warrants a dedicated post.
Bra fitters advise (well, they’d demand it if they could) that the center gore of your bra tack to, or be firmly touching, your sternum.
WHERE IN THE WORLD IS CARMEN SANDIEGO YOUR STERNUM??
For that matter, what is it there for?
First, location: It’s in the center of your chest, between your breasts! (If you do not have breasts, then they are between where your hypothetical breasts would be in those situations when you have hypothetical breasts.) Your ribcage is basically two mirror image half-cages, right? (Right?) They are symmetrical with a vertical line of symmetry going from your chin to your navel The sternum is the flat bone that runs along that line of symmetry, connecting the two ribcage halves. (It’ll be positioned upwards from the lowest point in your ribcage, because your lower ribs angle up before meeting. The sternum is not nearly as long as your full ribcage. )
What is it for?
From the point of view of a Googler (read: not a medical professional but good at looking things up online): it supports and is the core for your clavicles/collarbones and your ribcage. You know, the ribcage that protects your heart and any other vital organs hanging out in that vicinity? That one.
Since it’s kind of… in the middle of your body… beneath skin and tissue… your bra’s not exactly going to have direct interaction with the actual sternum bone. When we say “tacking to your sternum”, we mean it should be firmly touching that location marked in red in the above diagram, on your chest.
The sternum is also called the breastbone.
I’ll ask my nursing friends for any input on this cute primitive-dagger-shaped bone, see if there’s anything interesting on their front.
Sources: Yahoo Education ; The Free Dictionary
CurvyHK 
Funny thing about “flat against the sternum’ is that if you are wearing a plunge bra, wires do not reach breastbone and it’s more like “flat against solar plexus”.
May be we need a better rule.