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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.

The transition muscle between the palatopharyngeus (PP) and the superior constrictor of the pharynx (SCP) encircles the pharyngeal isthmus from behind and is designated as the palatopharyngeal sphincter (PPS). The PPS is inferred to play important roles for velopharyngeal closure, but its existence remains controversial and its roles have been regarded as being played by the SCP. The present study aimed to clarify the anatomical status and functional implications of the PPS. Macroscopic and microscopic examinations were performed on 39 and 4 cadavers, respectively. In the former, the bilateral PPSs and their adjacent structures were exposed from outside and/or inside. In the latter, the velums embedded in paraffin were cut into frontal or sagittal sections and alternately processed with HE and Azan stains. The PPS originated from the nasal aspect of the lateral half of the palatine aponeurosis and the inferior margin of the medial pterygoid plate and was distinguishable from the PP descending in and along the palatopharyngeal arch and the cranialmost portion of the SCP in its origin. It passed dorsally on the lateral side of the levator veli palatini and traversed around the salpingopharyngeal fold running longitudinally. It then entered below the SCP and ran toward the pharyngeal raphe with SCP muscle fibers intermingled. The PPS is a muscle distinct from the SCP. Its contraction produces Passavant’s ridge and conceivably enhances the efficiency of velopharyngeal closure by pressing the salpingopharyngeal fold and the musculus uvulae ridge against the velum.

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 oral cavity is a space bound anteriorly and laterally by the lips and cheeks, superiorly, by the palate and inferiorly by a muscular floor. It opens externally through the mouth, whereas posteriorly it is continuous with the pharynx through the isthmus of the fauces. The alveolar processes and the teeth divide the mouth into two parts: the vestibule, external to the teeth, and the oral cavity proper internal to the teeth.

Background Recent studies suggest advantages of muscle relaxants for facemask ventilation. However, direct effects of muscle relaxants on mask ventilation remain unclear because these studies did not control mechanical factors influencing ventilation. We tested a hypothesis that muscle relaxants, either rocuronium or succinylcholine, improve mask ventilation. Methods In anesthetized adult persons with normal upper airway anatomy, tidal volumes during facemask ventilation were measured while maintaining the neutral head and mandible positions and the airway pressures of a ventilator before and during muscle paralysis induced by either rocuronium (n=14) or succinylcholine (n=17). Tidal volumes of oral and nasal airway routes were separately measured with a custom-made oronasal portioning full facemask. Behavior of the oral airway was observed by an endoscope in six additional subjects receiving succinylcholine. Results Total, oral, and nasal tidal volumes did not significantly change at complete muscle paralysis with rocuronium. In contrast, succinylcholine significantly increased total tidal volumes at 60 s after its administration (mean±SD; 4.2±2.1 vs. 5.4±2.6 ml/kg, P=0.02) because of increases of ventilation through both airway routes. Abrupt tidal volume increase occurred more through oral airway route than nasal route. Dilation of the space at the isthmus of the fauces was endoscopically observed during pharyngeal fasciculation in all six subjects. Conclusions Rocuronium did not deteriorate facemask ventilation, and it was improved after succinylcholine administration in association with airway dilation during pharyngeal fasciculation. This effect continued to a lesser degree after resolution of the fasciculation.

The oral cavity or mouth is the space bounded anteriorly by the lips, laterally by the cheeks and superiorly by the palate. The floor is muscular with the tongue lying posteriorly and the two mylohyoid muscles joined in the midline anteriorly. The mouth opens posteriorly into the oropharynx through the isthmus of the fauces {fauces — throat, Latin) which is bounded laterally by the palatoglossal folds. The space between the cheeks externally and the teeth and alveolar processes of the maxilla and mandible internally, is called the vestibule of the mouth. When the teeth are together the vestibule communicates behind the last molar teeth with the oral cavity proper, the part of the mouth within the alveolar processes.

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