Look in a mirror and say the sounds in these words: ” ea”(scream), “i” (flip), “e” (jet), “a” (tan). What do you notice about the jaw? It gets wider and wider for every word.
Look closely at your tongue and you can see for each word the tongue gets more deflated with every word (from scream to tan). The midline of the tongue actually deflates like a beachball on steroids when you transition from an “e” to an “a” sound.