be the conditioning. The conchae are three shelf-like projections that extend from the
lateral wall of each nasal chamber. Thus, a superior, a middle, and an inferior concha
are found on each side. During ordinary breathing, the air enters the vestibules of the
nose and passes through the lower portions of the nasal chambers in direct contact with
the inferior and middle conchae.
d. Olfactory Epithelium. As the air passes through the nasal chambers, some
of the air reaches the superior recesses of the nasal chambers. In these superior
recesses is found the olfactory epithelium. The olfactory epithelium contains special
hair cells that can detect individual molecules found in the air. Thus, the sense of smell
(olfaction), tests the quality of inflowing air.
e. Paranasal Sinuses. Connected with each nasal chamber are cavities found
in the middle layer of various skull bones. These cavities are the paranasal sinuses.
Like the nasal chambers, they are lined with a continuation of the mucoperiosteum.
Each paranasal sinus is named according to the bone in which it is located. The
function of the paranasal sinuses is unknown.
The two nasal chambers are continuous posteriorly with a single cavity known as
a. Pharyngeal Tonsils ("Adenoids"). The pharyngeal tonsils are a pair of
lymphoid aggregates in the upper posterior recess of the nasopharynx.
b. Auditory (Pharyngeotympanic or Eustachian) Tubes. On each lateral wall
of the nasopharynx is a small mound with a slit-like opening. This is the opening of the
auditory tube, which passes laterally to the middle ear cavity. Because of this tube, the
air pressures are kept equal on the inner and outer sides of the tympanic membrane
c. Soft Palate. The floor of the nasopharynx is the soft palate. The soft palate
is a musculomembranous structure. (Unlike the soft palate, the hard palate is bony.
The hard palate forms the floor of the nasal chambers and the roof of the oral cavity.)
7-24. PHARYNX AND FUNCTION OF SOFT PALATE
The nasopharynx (of the respiratory system) and the oropharynx (of the digestive
system) are continuous posteriorly with the pharynx proper. During swallowing, the soft
palate is raised like a trap door to close off the upper air passageways. This prevents
movement of food into the upper air passageways.