Insertion pharyngeal raphe Dorlands
/Elsevier m_22/12548631 | Actions Swallowing | |
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Origin cricoid and thyroid cartilage Nerve Pharyngeal plexus of vagus nerve Latin musculus constrictor pharyngis inferior | ||
The Inferior pharyngeal constrictor, the thickest of the three constrictors, arises from the sides of the cricoid and thyroid cartilage. Similarly to the superior and middle pharyngeal constrictor muscles, it is innervated by the vagus nerve (cranial nerve X), specifically, by branches from the pharyngeal plexus and by neuronal branches from the recurrent laryngeal nerve.
Contents
Origin and insertion
The muscle is composed of two parts. The first (and more superior) arising from the thyroid cartilage (thyropharyngeal part) and the second arising from the cricoid cartilage (cricopharyngeal part).
From these origins the fibers spread backward and medialward to be inserted with the muscle of the opposite side into the fibrous pharyngeal raphe in the posterior median line of the pharynx.
The inferior fibers are horizontal and continuous with the circular fibers of the esophagus; the rest ascend, increasing in obliquity, and overlap the Constrictor medius.
Action
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 into the esophagus. During deglutition, they contract and cause peristaltic movement in the pharynx.
Role in human disease
Uncoordinated contraction, and/or Cricopharyngeal Spasm and/or impaired relaxation of this muscle are currently considered the main factors in development of a Zenker's diverticulum. Zenker's diverticulum develops between the two bellies of the inferior constrictor (Thyropharyngeal and Cricopharyngeal) in a small gap called Killian's dehiscence. A diverticulum can form where a balloon of mucosa becomes trapped outside the pharyngeal boundaries. Food or other materials may reside here, which may lead to infection.
Motor incoordination of the cricopharyngeus can cause difficulty swallowing.