When a person hears and understands words, and speaks, how do the body and brain work?

Exchanging language involves: (1) the ears receiving sound; (2) the brain identifying the sound, understanding its meaning, and assembling the content, words, and sentences to convey; (3) the nervous system planning the speech movements and sending commands to the respiratory organs, throat, tongue, lips, and so on; (4) breathing pushing out air, the vocal cords producing voice, the mouth and nose adding resonance, and the tongue, lips, and jaw forming vowels and consonants; and (5) hearing one's own voice and adjusting pronunciation, volume, and speed. These aren't separate boxes but a network that exchanges information with each other. It's not that strengthening just one part is enough; evaluation is done according to the symptoms of concern—hearing, snoring or mouth breathing, voice, pronunciation, comprehension, and expression. You can't self-diagnose a cause from this explanation alone.