<P> The entire lingual surface and the apical portion of the laryngeal surface (since it is vulnerable to abrasion due to its relation to the digestive tract) are covered by stratified squamous non-keratinized epithelium . However, some parts of the laryngeal surface, which is in relation to the respiratory system, has respiratory epithelium: pseudostratified, ciliated columnar cells and mucus secreting goblet cells . </P> <P> The epiglottis arises from the fourth pharyngeal arch . It can be seen as a distinct structure later than the other cartilage of the pharynx, visible around the fifth month of development . </P> <P> The epiglottis is normally pointed upward during breathing with its underside functioning as part of the pharynx . During swallowing, elevation of the hyoid bone draws the larynx upward; as a result, the epiglottis folds down to a more horizontal position, with its superior side functioning as part of the pharynx . In this manner, the epiglottis prevents food from going into the trachea and instead directs it to the esophagus, which is at the back . Should food or liquid enter the windpipe due to the epiglottis failing to close properly, the gag reflex is induced to protect the respiratory system . </P> <P> The glossopharyngeal nerve (CN IX) sends fibers to the upper epiglottis that contribute to the afferent limb of the gag reflex . (The gag reflex is variable in people from a limited to a hypersensitive response .) The superior laryngeal branch of the vagus nerve (CN X) sends fibers to the lower epiglottis that contribute to the efferent limb of the cough reflex . This initiates an attempt to try to dislodge the food or liquid from the windpipe . </P>

What is the purpose of the epiglottis in the respiratory system of humans