ANATOMY OF THE NASOPHARYNX (OR POST-NASAL SPACE)
Below, the nasopharynx communicates with the oropharynx, the next part of the pharynx, which lies behind the oral cavity and contains the tonsils. The two are partially separated by the soft palate. This muscular structure is attached to the posterior border of the hard palate (which forms the bony roof of the mouth), and at rest it hangs down like a curtain in the upper part of the oropharynx. It is characterised by two flat, lateral parts and a central elongation into the uvula, a slightly globular structure familiar to anyone who has ever examined the back of his own throat. While breathing through the nose, the soft palate hangs loosely and there is an open communication between the nasopharynx and the oropharynx. When swallowing, the soft palate, which is a muscular structure, is drawn sharply backwards and forms a seal with the posterior wall of the pharynx at the junction between the post-nasal space and the oropharynx. Within the wall there is a roughly semicircular ridge of muscle which contracts to meet the palate and form a complete seal, so that neither food nor liquid escapes into the back of the nose during the act of swallowing.