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Effective ‘valving’ in the upper aerodigestive tract (UAT) is essential to temporarily separate the digestive and respiratory pathways. Marine mammals are largely dedicated to feeding underwater, and in many cases swallowing prey whole. In seals, little work has been done to explore the anatomy and function of the upper aerodigestive tract in the context of valving mechanisms that function to separate food and air pathways. Here we use videofluoroscopy, gross dissection, histology and CT renderings to explore the anatomy of the larynx and soft palate in the harbour seal (Phoca vitulina), and generate models for how valving mechanisms in the head and neck may function during breathing, phonating, diving and swallowing. Harbour seals have an elevated larynx and the epiglottis may rise above the level of the soft palate, particularly in pups when sucking. In addition, the corniculate and arytenoid cartilages with associated muscles form most of the lateral margins of the laryngeal inlet and vestibule, and move independently to facilitate airway closure. The corniculate cartilages flex over the laryngeal inlet beneath the epiglottis to completely close the laryngeal vestibule and inlet. The vocal folds are thick and muscular and the medial margin of the folds contains a small vocal ligament. The soft palate has well-defined levator veli palatini muscles that likely function to elevate the palate and close the pharyngeal isthmus during feeding. Our results support the conclusion that harbour seals have evolved UAT valving mechanisms as adaptations to a marine environment that are not seen in terrestrial carnivores.

Background For soft palate defects of more than two-thirds, we previously described the bent anterolateral thigh (ALT) method in which the pharyngeal isthmus was reconstructed as a tunnel structure. In this study, we compared the new “tunnel structure” reconstruction in our bent ALT flap method and the traditional “port structure” reconstruction. Methods From April 2010 to March 2015, 25 patients in Saitama Cancer Center (Saitama, Japan) underwent oropharyngeal tumor resection including soft palate resection. In patients who had soft palate resection of less than two-thirds, the Gehanno method was performed in 10 patients (the data were shown as a comparison). In patients who had soft palate resection of more than two-thirds, the pharyngeal isthmus was reconstructed as a tunnel structure using the bent ALT flap method in eight patients and as a port structure in seven patients. The functional outcomes were assessed by interviewing patients about their symptoms and measuring the standard articulation test. Results Postoperative function was favorably maintained at equal levels in the tunnel structure reconstruction group and the Gehanno method group at approximately 12 months postoperation. However, in most patients in the port structure reconstruction group, the pharyngeal isthmus became larger after 12 months postoperation and the articulation test was significantly worse than the Gehanno group and the tunnel group. Conclusion The bent ALT flap method had superior results to the conventional method. Thus the pharyngeal isthmus should be reconstructed as a tunnel structure for patients with soft palate defects of more than two-thirds.

The palatopharyngeus (PP) extends throughout the entire length of the pharynx and probably plays an important role in deglutition, but its spatial distribution remains undefined in some respects. This study was designed to clarify the exact distribution of the PP indispensable for understanding its functions. Using 50 cadavers, the PP and its neighboring muscles were bilaterally exposed in both surfaces of the pharynx. The PP was composed of two divisions: longitudinal and transverse. It is already known that the longitudinal PP is divided into two fasciculi sandwiching the levator veli palatini (LVP) immediately after originating from the palatine aponeurosis. However, we newly discovered a fasciculus originating from the uvula, and further regarded the salpingopharyngeus as another fasciculus of origin. The four fasciculi united to descend through the palatopharyngeal arch and inserted into the thyroid cartilage and beneath the mucosa of the hypopharynx. The transverse PP occupied a location transitional between the PP and superior constrictor (SC), where it originated from the palatine aponeurosis and passed dorsally to encircle the pharyngeal isthmus and reach the pharyngeal raphe. Although whether it belongs to the PP or SC has remained controversial, we regarded it as a portion of the PP from the evolutionary perspective and proposed anatomical criteria for differentiating it from the SC. The wide distribution of the PP suggests that it acts not only to elevate the pharynx or depress the soft palate, but also as a nasopharyngeal sphincter when closing the pharyngeal isthmus.

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