I remember one time in high school (7th Form, no less) having to explain to a classmate where meat comes from:
"No, you know -- muscle tissue. That's the bit of an animal that we eat -- its muscles."
"Is it? Gross!"
"Well what part did you think we eat?"
"Just the... stuff... you know, the stuff that goes in between all the other bits..."
In his mind, "meat" was seemingly an extra type of generic body tissue that served no purpose other than to be cut out and eaten by humans.
I'm not actually sure what caused me to recall that anecdote recently, although it always does good to reflect that teenage boys are fucking stupid sometimes.