The sternum is the flat bone in the center of your chest that connects your ribs. If you press on the middle of your chest, you can feel it: a hard, smooth surface running from the base of your neck down to where your ribs end. The sternum acts like an anchor point, holding the front parts of your ribs in place and protecting the heart and lungs behind it.

Your sternum consists of three separate sections that fuse together as you grow: the top part (where your collarbones meet), the long middle section (where most of your ribs attach), and a small piece at the bottom. Together, they form what looks like a narrow shield over your chest.

Doctors and paramedics pay close attention to the sternum during CPR, because pressing on it correctly helps pump blood through the body when someone's heart has stopped beating. Athletes sometimes protect their sternum with chest guards in sports like baseball or hockey, since a hard impact there can be painful and dangerous.