Book 33, Question 6
What is a diaphragm, and why do mammals have one?
The diaphragm is a dome-shaped muscle under your lungs.
When you breathe in, it pulls down and gives your lungs room to fill with air. When you breathe out, it relaxes and moves up. Every mammal has one, and it helps them breathe deeply and steadily. Sometimes the diaphragm twitches, and that’s what makes a hiccup.