The inferior pharyngeal constrictor muscle is composed of two parts. The first part (and more superior) arises from the
thyroid cartilage (
thyropharyngeal part), and the second part arises from the
cricoid cartilage (
cricopharyngeal part). • On the
thyroid cartilage, it arises from the
oblique line on the side of the
lamina, from the surface behind this nearly as far as the posterior border and from the
inferior horn of the thyroid cartilage. • From the
cricoid cartilage, it arises in the interval between the
cricothyroid muscle in front, and the articular facet for the inferior horn of the thyroid cartilage behind. 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 thyropharyngeal part mainly uses type 2 fibres (anaerobic), while the cricopharyngeal part mainly uses type 1 fibres (aerobic). Fibre type may change after birth. The inferior fibers are horizontal and continuous with the circular fibers of the
esophagus; the rest ascend, increasing in obliquity, and overlap the
middle pharyngeal constrictor muscle. The cricopharyngeal part is synonymous with the
upper esophageal sphincter (UES), which controls the opening of the cervical esophagus. It is sometimes referred to as the cricopharyngeal inlet.
Nerve supply The inferior pharyngeal constrictor muscle can be supplied by branches from the
pharyngeal plexus, All these branches and nerves come from the
vagus nerve (CN X). == Function ==