swallowing or deglutition is the process
by which food passes from the mouth
through the pharynx and
into the esophagus as simple as it might seem to
healthy people swallowing is actually a
very complex action that requires an
extremely precise coordination withbreathing since both of these processes
share the same entrance the pharynx
failure to coordinate would result in
choking or pulmonary aspirationswallowing involves over 20 muscles of
the mouth throat and esophagus
which are controlled by several cortical areas and by the swallowing centers in the brainstem
the brain communicates with the muscles through several cranialnerves
swallowing consists of three phases. oral or buccal phase this
is the voluntary part of swallowing. the food is
moistened with saliva and chewed
a food bolus is formed
and the tongue pushes it to the back of the throat the pharynx.
this process is under neural control of several areas of cerebral cortex
including the motor cortex
pharyngeal phase starts with the stimulation of tactile receptors
in the oral pharynx by
the food bolus. the swallow reflex
is initiated and is under involuntary neuromuscular control.
the followingactions are taken to ensure
the passage of food or drink into the esophagus.
the tongue blocks the oral cavity to prevent food from going back to the mouth.
the soft palate blocks entry to the nasal cavity.
the vocal folds closed to protect the airway to the lungs.
the larynx is pulled up with the epiglottis flipping over covering the entry to the trachea
this is the most important step
since entry of food or drink into the lungs
may potentially be life-threatening.
the upper esophageal sphincter opens to allow passage to the esophagus.
esophageal phase the food bolus is
propelled down the esophagus byperistalsis
a wave of muscluar contraction that pushes the bolus ahead of it.
the larynx moves down back to the original position