[1] From these origins, the fibers spread backward and medially to insert with the muscle of the opposite side into the fibrous pharyngeal raphe in the posterior median line of the pharynx.

The cricopharyngeal part is synonymous with the upper esophageal sphincter (UES), which controls the opening of the cervical esophagus.

[6] The inferior pharyngeal constrictor muscle has a broad role in moving the lower part of the pharynx.

In extreme cases, this can be related to retrograde cricopharyngeal dysfunction (R-CPD) which causes the inability to burp; this is in part due to the muscle not being able to relax.

[9][10] The inferior pharyngeal constrictor muscle may be damaged by chemotherapy-intensity modulated radiotherapy.

[11] This article incorporates text in the public domain from page 1142 of the 20th edition of Gray's Anatomy (1918)