To see how the throat of a singer is different than that of someone who doesn't sing you have to watch the singer belt out a tune while inside an MRI machine, so you can see how the vocal tract changes as they sing.
Vocologist Tyley Ross sang the Puccini aria "Nessun Dorma" in four different styles inside an MRI machine at the NYU Langone Voice Center so we can see how the vocal tract changes when he sings in different styles:
What you’re looking at here are comparative images of the same vowel being sung at the same moment in each vocal style. …take a moment to see for yourself how the anatomical features of the vocal tract that we can see here align differently in each style. How does the tongue position differently? How about the view on the mouth opening? How about the height of the larynx?
-Via Laughing Squid