The oral preparatory
This part of the
swallow is voluntary. It is a mechanical phase that can be
by-passed by dropping liquid or food into the back of the
In this stage, the
food is chewed into smaller pieces and tasted. It is also
mixed with saliva from three pairs of salivary glands, which
are innervated by the glossopharyngeal nerve. The food and
saliva form a bolus of material.
The bolus is kept
in the front of the mouth, against the hard palate by the
tongue. The front of the tongue is elevated with its tip on
the alveolar ridge. The back of the tongue is elevated and
the soft palate is pulled anteriorly against it to keep the
food in the oral cavity (the airway is open and nasal
breathing continues during this phase). Labial seal is
maintained to prevent food from leaking out of the mouth.
Buccal muscles are tense. This prevents pocketing of food.
Duration of the oral-preparatory stage is variable
(Logemann, 1983,1989, 1997).
The oral transport
This stage of the
swallow is also voluntary. It starts with the jaws and lips
closed, and the tongue tip on the alveolar ridge. The
pattern-elicited response is initiated at the end of this
reflexively inhibited at the beginning of this stage. The
food is moved to the back of the mouth by the tongue via an
anterior to posterior rolling motion. The anterior portion
of the tongue is retracted and depressed while the posterior
portion is retracted and elevated against the hard palate.
When the bolus passes the anterior faucial pillars/touches
the posterior wall of the pharynx, the oral stage ends and
the pharyngeal stage begins as the tongue driving force or
the tongue's plunger action, forces the bolus into the
pharynx. Logemann (1997) describes the "pharyngeal tongue"
which extends from the velum to the hyoid bone and
valleculae. The "oral tongue" which extends from the tip to
the back, adjacent to the velum, functions during the oral
stage of the swallow while the "pharyngeal tongue" functions
during the pharyngeal stage. The oral transport stage lasts
one second (Logemann, 1989, 1998; Dobie, 1978).
(Logemann, 1989, 1997, 1998; Cherney, 1994)
stage of the swallow is involuntary. It is the most critical
stage of the swallow; airway closure must occur to prevent
the bolus from entering the respiratory system. A number of
things occur almost simultaneously: .
information from receptors in the back of the mouth and
in the pharynx goes to the swallowing center in the
medulla via CN. IX. The palatopharyngeal folds pull
together medially to form a slit in the upper pharynx.
The bolus passes through this slit.
- The velum is
raised, primarily by the levator and tensor veli palatini
muscles. This prevents the entry of food into the
nasopharynx. The narrowing of the upper pharynx due to
the contraction of superior pharyngeal constrictor muscle
helps to close the velopharyngeal port.
- The tongue is
retracted, preventing the food from re-entering the
occur simultaneously to protect the airway. (Obviously,
inspiration is inhibited during the pharyngeal stage of the
- The larynx and
the hyoid bone are pulled both upward and forward. This
movement enlarges the pharynx. It also creates a vacuum
in the hypopharynx, pulling the bolus downward. Finally,
it contributes to the relaxation of the cricopharyngeous
muscle (Dobie, 1978; Logemann, 1983, 1989, 1997)
- The true and
false vocal folds adduct. (Closure begins at the level of
the true vocal folds and progresses up to the false vocal
folds and then to the ari-epiglottic folds.)
- The epiglottis
drops down over the top of the larynx, protecting the
airway and diverting the bolus into the pyriform sinuses.
The bolus passes down on both sides of the epiglottis. If
the bolus is liquid, the epiglottis acts as a ledge to
slow its movement through the pharynx, giving the vocal
folds time to adduct and the larynx time to elevate.
(Nevertheless, the action of the epiglottis is the least
important of these three movements.)
cause food to move down the pharynx during the rest of the
pharyngeal stage (Cherney, et al., 1994; Logemann, 1983,
- The tongue
driving force using the "pharyngeal tongue"
- The stripping
action of the pharyngeal constrictors
- The presence
of negative pressure in the laryngopharynx-the laryngeal phase of the pharyngeal stage
It is believed by
some that the tongue driving force (TDF) is the most
important of these factors. This generates pressure in the
stage ends when the cricopharyngus muscle relaxes, allowing
the bolus to enter the esophagus. It is believed that the
following three factors affect the opening of the p.e.
segment, although the process is not currently
- Innervation by
the vagus nerve
- The timing of
the stripping action in the pharynx may somehow trigger
the relaxation of the p.e. segment.
- The elevation
of the larynx may pull the muscle upward, causing it to
open by stretching it and therefore causing it to
In this phase,
which is of course involuntary, the bolus is moved down the
esophagus via peristaltic wave motion with some help from
At the beginning
of the phase, the larynx lowers, returning to its normal
position. The cricopharyngeus muscle contracts to prevent
reflux and respiration resumes.
normally lasts between eight and twenty seconds, but in
elderly individuals peristalsis is slower (Logemann, 1989,
1997; Dobie, 1978).
problems can cause the reflux of food back into the pharynx,
leading to aspiration. Speech pathologists do not treat
esophageal problems, but should be aware of them, and be
able to differentiate them from problems that are within
their scope of practice.
*** Note that 90%
of the swallow occurs during expiration; an apneal pause
between 1 and 3.5 seconds in duration occurs during the oral
and pharyngeal stages (Logemann, 1989; 1997).