List the roles of each of the three anatomical regions of the pharynx in respiration.

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.