Complex sentence: The superior pharyngeal constrictor muscle is a quadrilateral muscle, thinner and paler than the inferior pharyngeal constrictor muscle and middle pharyngeal constrictor muscle.
Split into simpler sentences: The superior pharyngeal constrictor muscle is a muscle in the pharynx. The muscle is a quadrilateral muscle, thinner and paler than the inferior pharyngeal constrictor muscle and middle pharyngeal constrictor muscle.