|ISSUES IN THE ANATOMY AND PHYSIOLOGY OF
SWALLOWING: IMPACT ON THE
ASSESSMENT AND TREATMENT OF CHILDREN WITH DYSPHAGIA
Complex Anatomy can be Viewed as a Series of Tubes
and Cavities with a Division by Function
The swallowing system is comprised of a single tube
which widens in the upper region to form cavities. The
tube divides at the lower end into a tube for feeding
(i.e. the esophagus) and a tube for breathing (i.e. the
trachea). Each cavity, formed by the enlargement of a
portion of the tube serves initially either the function
of feeding (i.e. oral cavity, vallecula, pyriform sinus)
or breathing (i.e. nasal cavity).
The Function of Both the Feeding and Respiratory
Systems Can be Modified by the Use of Valves
Each system contains a series of valves which change
the shape or configuration of the system or protect it.
Valves created by the lips and tongue keep food in the
mouth and in place prior to swallowing. The valve created
by the cricopharyngeous muscle at the top of the
esophagus keeps air out of the digestive system during
breathing. The valve created by the soft palate keeps
food out of the nasal airway during swallowing. The
valves created by the false and true vocal folds and the
epiglottis prevent food from entering the airway during
Shared Pathways Exist between the Feeding and
The feeding and respiratory systems share a portion of
the pharynx between the area behind the tongue and the
area at the entrance to the larynx and the entrance to
Since a Shared System Exists, Valves are Used to
Support the Desired Activity and Protect the Alternate
During breathing the valves open to allow air to enter
the nose, larynx, and trachea and close to prevent air
from entering the esophagus and lower digestive tract.
During swallowing the valves open to allow food to enter
the digestive tract and prevent food from penetrating the
nose and larynx and entering the airway.
During swallowing the goal of the system is to move
food into the digestive system and keep it out of the
respiratory system. The following events occur rapidly
and often simultaneously to support this goal.
- Food is propelled from the front to the back of
the mouth during the oral stage of the swallow.
The lips and sides of the tongue serve as valves
to direct the food efficiently toward the
pharynx. The back of the tongue elevates and
moves food into the pharynx as the pharyngeal
swallow is triggered.
- The pharyngeal constrictors contract in a
peristaltic wave, moving the bolus downward.
- The soft palate elevates to prevent the bolus
from refluxing into the nasal cavity.
- The hyoid and larynx elevate and the epiglottis
moves downward to protect the entrance to the
airway. This movement of the hyoid also initiates
relaxation of the cricopharyngeus muscle and
opening of the esophagus.
- The aryepiglotic folds and the true and false
vocal folds contract, providing additional airway
- The bolus moves through the cricopharyngeal
sphincter into the esophagus. This sphincter
closes, preventing upward movement of the bolus.
- Peristaltic movement of the esophagus carries the
bolus to the stomach. The lower esophageal
sphincter closes to prevent gastroesophageal
During breathing the goal of the system is to move air
efficiently into the respiratory system and keep it out
of the digestive system. The following events support
- The soft palate relaxes allowing air to enter the
nose and pass downward toward the lungs.
- The false and true vocal folds remain relaxed and
open for the entry of air.
- The cricopharyngeus muscle sustains contraction
to close off the top of the esophagus and prevent
air from entering the digestive system.
The Infant is not an Anatomical Miniature of the
Proportional differences exist between the young
infant and the older infant, child, and adult. These
- The oral cavity is small in the newborn and is
totally filled by the tongue due to a small and
slightly retracted lower jaw.
- The newborn has a set of sucking pads in the
cheeks which provide stability during sucking.
- The soft palate and epiglottis are in contact at
rest, providing an additional valve at the back
of the oral cavity.
- The larynx and hyoid cartilage are higher in the
neck and closer to the base of the epiglottis,
providing added protection of the airway.
- The infantŐs eustachian tube runs horizontally
from the middle ear into the nasopharynx, rather
than its later vertical angle in the older child
IMPLICATIONS FOR THE CHILD
WITH SWALLOWING DYSFUNCTION
The Absence of a Swallowing Reflex Leaves the
If the swallowing reflex is not triggered by backward
movement of the bolus and/or intention, the airway
remains open and unprotected. The upper esophageal
sphincter remains closed, preventing food entrance into
the esophagus and indirectly biasing its movement into
the open airway.
Delay in Elicitation of the Swallowing Reflex
Places the Airway in a Risk Position
Difficulties with sensory awareness, inefficient
organization of the oral bolus, and problems with timing
and coordination of movement may cause portions of the
bolus to enter or remain in the pharynx during periods of
airway opening. This creates a risk of aspiration before,
during, or after the swallow has been triggered.
Small Cavities Formed by the Valleculae and
Pyriform Sinuses can Serve as Catching Pools for Portions
of the Bolus
Pooling of the bolus in the sulci or cavities formed
by the valleculae and pyriform sinuses can delay
penetration of the airway by the bolus. Because of this
delay, it can appear clinically as if the bolus were
swallowed. Entrance into the laryngeal vestibule or
penetration of the airway may be signalled by coughing or
choking that occurs during the 3rd or 4th small bolus.
The Shared Use of the Pharynx by Respiratory and
Feeding Systems Increases the Risk of Aspiration in
Children whose Respiratory Systems are Compromised.
Infants and children with primary respiratory
difficulties (i.e. respiratory distress syndrome,
bronchopulmonary dysplasia) often protect their
vulnerable respiratory systems through a central
inhibition of the swallowing reflex, or a voluntary
refusal to swallow. This may be observed even when the
child is receiving respiratory assistance through a
ventilator or additional oxygen.
The Infant Anatomical Differences Create Additional
Protective and Learning Systems which may not be Present
in the Older Infant or Child with Severe Swallowing
- The small infant oral cavity creates abundant
sensory input to the tongue, giving information
on spatial and movement relationships within the
mouth. This supports the lesser neurological
coordination of the young infant. When an infant
or child has developed anatomically without a
comparable development neurologically, the
evolving feeding coordination lacks the early
infant anatomical back-up system.
- The sucking pads provide additional stability of
the jaw and support a more efficient sucking
pattern as the infant gradually develops the
coordination of the jaw, lips, cheeks, and tongue
to support oral feeding. When an older child is
initially developing the sucking coordination of
the newborn, the sucking pads may be reduced or
absent. Thus, the early coordination lacks the
anatomical support available to the newborn with
this degree of oral control.
- When the soft palate and epiglottis grow away
from each other and are no longer in contact, the
baby looses a valve which helps keep food in the
mouth until the pharyngeal swallow is initiated.
The older infant or child with poor oral control
of the bolus may then have food fall over the
back of the tongue into the valleculae or airway
before the swallow is triggered.
- The airway has less anatomical protection as the
larynx assumes its lower position in the neck and
is not as directly protected by the epiglottis.
Since infants younger than 4-6 months have
additional airway protection, poor closure of the
airway or even a partial paralysis of the vocal
folds may not be as evident. When the anatomy no
longer gives additional protection for a
marginally coordinated swallowing mechanism,
coughing, choking or aspiration may occur.
- The horizontal positioning of the eustachian tube
places the infant at greater risk for ear
infections from food or liquid that refluxes
upward into the nasopharynx.
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Evans Morris, Ph.D.
1124 Roberts Mountain Road
Faber, Virginia 22938
This paper is a working
draft and multiple copies may not be reproduced
without prior written permission of the author
© Suzanne Evans Morris, 1998, Revised 2011 All Rights Reserved