The inferior pharyngeal constrictor has two functionally distinct parts. The thyropharyngeus constricts the hypopharynx during swallowing. The cricopharyngeus is the upper oesophageal sphincter, maintaining constant tone to prevent oesophago-pharyngeal reflux and relaxing briefly during swallowing to allow bolus passage. Cricopharyngeal dysfunction (failure to relax) produces the pharyngeal dysphagia of Zenker's diverticulum and post-stroke aspiration.
| Origin | Thyropharyngeus part: oblique line of the thyroid cartilage. Cricopharyngeus part: lateral arch of the cricoid cartilage |
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| Insertion | Median pharyngeal raphe (thyropharyngeus); wraps circularly around the pharyngo-oesophageal junction (cricopharyngeus — the upper oesophageal sphincter) |
| Nerve Supply | Pharyngeal plexus (IX, X) and recurrent laryngeal nerve (cricopharyngeus) |
| Blood Supply | Inferior thyroid artery |
| Actions | Thyropharyngeus: constricts the lower pharynx (hypopharynx); Cricopharyngeus: maintains the upper oesophageal sphincter tone (70-80 mmHg resting pressure); relaxes during swallowing to allow the bolus to enter the oesophagus |
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Cricopharyngeal myotomy (dividing the cricopharyngeus horizontally) is the definitive treatment for cricopharyngeal dysfunction. It can be performed open or endoscopically (CO2 laser division of the cricopharyngeus through the mouth). The recurrent laryngeal nerve runs immediately lateral to the cricopharyngeus and must be identified and protected.
The cricopharyngeus is palpable as a transverse bar just below the thyroid cartilage inferior border when the patient is relaxed and the neck is extended.
Cricopharyngeus failure to relax producing transfer dysphagia and aspiration managed with cricopharyngeal myotomy or botulinum toxin injection.
