Breastbone in a sentence as a noun

Why do birds have a huge keel-like breastbone on which equally huge and powerful flight muscles attach?

One particularly forceful Lundgren punch to Stallone's chest slammed his heart against his breastbone, causing the heart to swell and his breathing to become labored.

Breastbone definitions

noun

the flat bone that articulates with the clavicles and the first seven pairs of ribs

See also: sternum