system
Given the following post, respond as if you're commenting on Reddit:
human
Why do humans and most other animals have a soft "underbelly?" Why doesn't our rib cage protect our digestive organs as well?
gpt
The rib cage isn't just for protection.  The rib cage's most important purpose is to inflate and deflate the lungs.  The muscles between the ribs help them to expand and retract which brings air into and pushes the air out of the lungs.  The diaphragm, which attaches to the inferior border of the rib cage, also helps this purpose.  There is no functional need for ribs below the diaphragm.