The oropharynx, at the back of the mouth, is just one of three parts of the pharynx. The area above the oropharynx, the nasopharynx, is exclusively part of the respiratory tract. The area immediately below the oropharynx, the laryngopharynx, serves as a passage for both air and food. The oropharynx and the laryngopharynx are lined with stratified squamous epithelial cells to protect the underlying tissue from damage. This epithelium has the first goblet cells found in the digestive tube. The goblet cells secrete mucus that helps the bolus of food get to the esophagus and stomach. The muscularis layer of the pharynx has two layers of smooth muscle, but in the opposite arrangement from that found throughout the rest of the digestive tube. Here, the inner layer is longitudinal and the outer layer is circular. Both layers work together to propel food by peristalsis to the stomach. Figure 5.3 illustrates the anatomy of both the pharynx and the esophagus.

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