It acts to propel a bolus downwards along the pharynx towards the esophagus, facilitating swallowing.

[1] Two parts of the middle pharyngeal constrictor muscle are distinguished according to its sites of origin: The muscle inserts (posteriorly) into the pharyngeal raphe,[1] blending with its contralateral partner at the midline.

[citation needed] The contraction of the muscle constricts the middle portion of the pharynx.

[1] The muscle contracts during swallowing:[1] as soon as the bolus of food is received in the pharynx, the elevator muscles relax, the pharynx descends, and the constrictors contract upon the bolus, and convey it downward towards the esophagus.

[4] This article incorporates text in the public domain from page 1143 of the 20th edition of Gray's Anatomy (1918)