The cricopharyngeus (or cricopharyngeal muscle) is one of the two parts comprising the inferior pharyngeal constrictor. The other is the thyropharyngeal muscle (or thryropharyngeus). The cricopharyngeus is the one arising from the cricoid cartilage whereas the thyropharyngeus arises from the thyroid cartilage. These two muscles are involved in swallowing. The cricopharyngeus is completely open to allow an easy passage of the bolus from the pharynx down to the cervical esophagus whereas closed between swallows. Failure of the cricopharyngeus to relax can cause difficulty in swallowing and to cricopharyngeal achalasia. When cricopharyngeus does not relax completely, opens late, or closes early, a portion of the bolus may be trapped on top of it. 1
1Jones, B. (2003). Normal and abnormal swallowing: imaging in diagnosis and therapy (2nd ed.). New York: Springer.