<P> The oropharynx lies behind the oral cavity, extending from the uvula to the level of the hyoid bone . It opens anteriorly, through the isthmus faucium, into the mouth, while in its lateral wall, between the palatoglossal arch and the palatopharyngeal arch, is the palatine tonsil . The anterior wall consists of the base of the tongue and the epiglottic vallecula; the lateral wall is made up of the tonsil, tonsillar fossa, and tonsillar (faucial) pillars; the superior wall consists of the inferior surface of the soft palate and the uvula . Because both food and air pass through the pharynx, a flap of connective tissue called the epiglottis closes over the glottis when food is swallowed to prevent aspiration . The oropharynx is lined by non-keratinised squamous stratified epithelium . </P> <P> The HACEK organisms (Haemophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella) are part of the normal oropharyngeal flora, which grow slowly, prefer a carbon dioxide - enriched atmosphere, and share an enhanced capacity to produce endocardial infections, especially in young children . Fusobacterium is a pathogen . </P> <P> The laryngopharynx, (Latin: pars laryngea pharyngis), also known as hypopharynx, is the caudal part of pharynx; it is the part of the throat that connects to the esophagus . It lies inferior to the epiglottis and extends to the location where this common pathway diverges into the respiratory (larynx) and digestive (esophagus) pathways . At that point, the laryngopharynx is continuous with the esophagus posteriorly . The esophagus conducts food and fluids to the stomach; air enters the larynx anteriorly . During swallowing, food has the "right of way", and air passage temporarily stops . Corresponding roughly to the area located between the 4th and 6th cervical vertebrae, the superior boundary of the laryngopharynx is at the level of the hyoid bone . The laryngopharynx includes three major sites: the pyriform sinus, postcricoid area, and the posterior pharyngeal wall . Like the oropharynx above it, the laryngopharynx serves as a passageway for food and air and is lined with a stratified squamous epithelium . It is innervated by the pharyngeal plexus . </P> <P> The vascular supply to the laryngopharynx includes the superior thyroid artery, the lingual artery and the ascending pharyngeal artery . The primary neural supply is from both the vagus and glossopharyngeal nerves . The vagus nerve provides a branch termed "Arnolds Nerve" which also supplies the external auditory canal, thus laryngopharyngeal cancer can result in referred otalgia . This nerve is also responsible for the ear - cough reflex in which stimulation of the ear canal results in a person coughing . </P>

What is the function of the nasopharynx in the respiratory system