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The pharynx (also depicted in Chapter 3. Gastronintestinal System, Pharynx) is connected to the nasal and oral cavities and contains the entrances to the Eustachian tube, the larynx, and the esophagus (see Diagram of Upper Respiratory System – In Situ). The entrance to the larynx is closed off by the epiglottis during swallowing to prevent choking. The pharynx is lined by stratified squamous epithelium. The lamina propria of the pharynx contains minor salivary glands. The epiglottis projects into the pharynx and consists of, from outside to inside, stratified squamous epithelium, a lamina propria of fibroelastic connective tissue that lacks glands, perichondrium, and a core of elastic cartilage with elastic and reticular fibers.
The 4X micrograph shows the connection between the pharynx and the larynx and esophagus, the epiglottis at the entrance of the larynx, and soft palate separation between the nasal cavity and the pharynx. In the 10X micrograph the respiratory epithelium of the larynx is visible. The 20X and 40X micrographs show details of the epiglottis: an elastic cartilage structure surrounded by perichondrium and lamina propria, which is covered by stratified squamous epithelium. The layers of the epithelium are visible in the 40X micrograph.
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