Simplify the following text for a Grade 15 native English-speaking person.
Original: The trapezius has three functional regions : the superior region ( descending part ) , which supports the weight of the arm ; the intermediate region ( transverse part ) , which retracts the scapulae ; and the inferior region ( ascending part ) , which medially rotates and depresses the scapulae .
Simplified: The trapezius has three functional regions : the superior region , which supports the weight of the arm ; the intermediate region , which retracts the scapulae ; and the inferior region , which rotates and depresses the scapulae .