The Journal
widest part of the pharynx and it is in
communication with the nasal cavity via the
choanae and with the middle ear cavities via the
Eustachian tubes.
The oropharynx can be subdivided into the
retropalatal pharynx, from the hard palate to the
caudal margin of the soft palate, and the
retroglossal pharynx, which extends from the
caudal margin of the soft palate to the base of
the epiglottis; and the hypopharynx is from the
base of the epiglottis to the larynx 5 .
The oropharynx, opening into the oral cavity by
an isthmus, extends from the second cervical
vertebra to the fourth cervical vertebra. The
laryngopharynx joins the oropharynx at the
level of pharyngoepiglottic fold and the hyoid,
and then it continues to the level of the sixth
cervical vertebra.
The nasopharynx and the oropharynx have
significant locations and functions because
both of them form a part of the unit in which
respiration and deglutition are carried out. The
nasal portion of the nasopharynx has bony
elements in its wall and is thus rigid, whereas
the pharyngeal part is contractile as a result of
the muscular nature of its wall. And they include
lymphoid tissue in their structures 2 .
Nasal obstruction secondary to hypertrophied
inferior turbinates, adenoidal pad hypertrophy,
and hypertrophy of the faucial tonsils can cause
chronic mouth breathing, loud snoring,
obstructive sleep apnea, excessive daytime
sleepiness, and even cor pulmonale. In this
situation, a number of postural changes, such
as open mandible posture, downward and
forward positioning of the tongue, and
extension of the head, can take place. If these
postural changes continue for a long period,
especially during the active growth stage,
dentofacial disorders at different levels of
severity can be seen, together with the
inadequate lip structure, long face syndrome,
35
and adenoidal facies2.
Heredity plays an important role in
determining the size and shape of the human
face and thus of the airway; however,
environment appears to play a major part in the
etiology of nasal obstruction. Normal upper
airway space is 15-20 mm while lower airway
space is 11-14 mm 6 .
As the nasopharyngeal space increases with
the age of the child and the lymphoid tissue on
the posterior wall of the nasopharynx usually
diminishes before puberty, it is helpful to obtain
standards for the sagittal size of the
nasopharyngeal airway at different ages.4
Some authors associated mouth breathing and
Class II malocclusions, and others reported
associations of vertical growth patterns with
obstruction of the upper and lower pharyngeal
airways concurrently with mouth breathing. If
this relationship actually exists, Class II
malocclusions and vertical growth patterns
must have natural anatomical predisposing
7-9
factors
Skeletal features such as retrusion of the
maxilla and mandible and vertical maxillary
excess in hyperdivergent patients may lead to
narrower anteroposterior dimensions of the
airway. On the other hand, the oropharyngeal
airway has been claimed to affect the growth of
the craniofacial structures.
According to the Balters' philosophy, Class II
malocclusions are a consequence of a
backward position of the tongue, disturbing the
cervical region. The respiratory function is
impeded in the region of larynx and there is thus
a faulty deglutition and mouth breathing. Class
III malocclusions are due to a more forward
position of the tongue and due to cervical
10
overdevelopment .
It has been reported by authors that the
midsagittal nasopharyngeal area and the
Vol. 14 No. 2
May-August 2018