The three anatomical regions of the pharynx are:
Nasopharynx - air and secretions from the nose travel through this passageway and connects with the oral pharynx on its path to the hypopharnx. The pharngeal tonsil is located near it so when it swells it may interfere was nasal respiration.
Oral pharynx (oropharynx) - the soft palate at the posterior of the oral cavity bounds it from the nasopharynx. When you breather through your mouth the air enteres the oral pharynx
Hypopharnyx - this is where the pathway of air food cross each other: air from the nasal cavity flows to the larynx, while food from the oral cavity is routed to the esophagus.
See link for a photo of the pharynx.
The Pharynx has three parts: the nasopharynx, the oropharynx and the laryngopharynx. At the base of the nasopharynx, structures called the soft palate and the pendulous uvula block the nasopharynx when food is swallowed so that it does not pass into the lungs. The mucous layer in the oropharynx traps any large particles in the air that we breathe which are not allowed to enter the lungs and instead pass with the mucous into the stomach. The laryngopharynx is a common pathway that allows both air as well as food to pass through to the lungs and stomach resp. In case the air goes to the stomach, we burp and food that goes to the lungs is expelled by coughing.