Although numerous studies have been performed on the function and dysfunction of the pharyngoesophageal segment, few studies have investigated features of the musculature in this area. Thus, the purpose of this study was to systematically examine the structure (gross anatomy and histology) in this area and to relate these findings to the functions of the pharyngoesophageal segment. Twenty-one autopsy and surgery patients underwent careful measurement and observation of 1. the vertical (cephalad-caudad) height of the cricopharyngeus muscle (CP); 2. the presence or absence of Killian's debiscence; and 3. the separation or blending of the CP with the upper esophageal circular muscles. Of the 21 subjects, muscle specimens were removed from 8 (4 autopsy, 4 surgical) to include a muscle strip from the upper esophageal circular muscles, CP, and inferior pharyngeal constrictor and submitted to a battery of histological and histochemical tests. Gross anatomic measurements of the vertical height of the CP were substantially longer than those reported elsewhere. Killian's dehiscence was shown to be present in fewer than one third of the specimens. Histology of these muscles also showed significant differences from the muscles discussed in other published reports, particularly when fresh and autopsy material were compared. These specialized muscles, therefore, require further detailed study.
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