Human pharynx

The pharynx (plural: pharynges) is the part of the neck and throat situated immediately posterior to the mouth and nasal cavity, and cranial to the esophagus, larynx, and trachea. It is part of the digestive system and respiratory system of many organisms.

Because both food and air pass through the pharynx, special adaptations are necessary to prevent choking or aspiration when food or liquid is swallowed. In humans the pharynx is important in vocalization.

Reference:
 * Stedman's Online Medical Dictionary, 27th Edition

Parts
The human pharynx is conventionally divided into three sections:
 * Nasopharynx, lying behind the nasal cavity. Postero-superiorly this extends from the level of the junction of the hard and soft palates to the base of skull, laterally to include the fossa of Rosenmuller. The inferior wall consists of the superior surface of the soft palate.
 * Oropharynx, which lies behind the oral cavity. The anterior wall consists of the base of the tongue and the 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.
 * Hypopharynx, also known as the laryngopharynx, which includes the pharyngo-oesophageal junction (postcricoid area), the piriform sinus, and the posterior pharyngeal wall. Like the oropharynx above it the hypopharynx serves as a passageway for food and air and is lined with a stratified squamous epithelium. It lies directly posterior to the upright epiglottis and extends to the larynx, where the respiratory and digestive pathways diverge. At that point the laryngopharynx is continuous with the esophpagus 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.