system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does a turtle’s shell grow while the turtle grows? What is it made of?
gpt
The shell is made up of panel-like things called scutes. With most types of turtles, these scutes shed periodically to allow bigger scutes to form. They are made out of keratin - same as human hair & nails.

Source: I’m a turtle fan.