Ch. 9
Physiology of Mastication
and Deglutition
Introductory Terms
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Dysphagia: A disorder of swallowing
Bolus: ball of food or liquid to be swallowed
Mastication: the process of preparing food for
swallowing
• Moving food onto the grinding surfaces of the teeth
• Chewing
• mixing it with saliva in preparation for swallowing
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Deglutition: the process of swallowing
• Both the two above concepts require integration of
lingual, velar, pharyngeal, facial muscle movement,
laryngeal adjustments, respiratory control
Introductory Terms
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Perioral region: around the mouth
Rooting Reflex: reflexive response of infant to
tactile stimulation of the cheek or lips, infant
turns toward stimulus, opens mouth
Sucking Reflex: tongue protrusion and retraction
in preparation for receipt of liquid; stimulated by
contact to the upper lip
Esophageal Reflux: esophageal regurgitation into
the hypopharynx
Nasal regurgitation: loss of food or liquid through
the nose
Peristaltic: Wavelike
Introductory Terms
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Oral Transit Time: time required to
move the bolus to the point of
initiation of the pharyngeal stage of
swallowing
Pharyngeal Transit Time: time
required to move the bolus from the
beginning of pharyngeal swallow to
the time the bolus enters the
esophagus
Organizational Patterns
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Oral Preparatory Stage
• Stage in which food is prepared for swallow
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Oral Stage
• Bolus transmitted to pharynx
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Pharyngeal Stage
• Bolus transmitted to the esophagus
• Numerous physiological responses
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Esophageal Stage
• Food is transported from the upper esophageal
region to the stomach
Deficit Patterns
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Oral Preparatory Stage
• Neuromuscular deficits
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Loss of sensation and awareness
Weak buccal musculature
Weak muscles of mastication may cause inadequqtely
chewed food
Weak lingual muscles may cause poor mixture of
saliva with food, inadequate bolus production,
difficulty compressing bolus onto hard palate
Weak soft palate muscles may cause the velum to
not be fully depressed, tongue not adequately
elevated in back, permitting food to escape into the
pharynx prior to initiation of pharyngeal reflexes
Food entering pharynx prior to a reflexive response
may reach the open airway and produce an
aspiration pneumonia
Deficit Patterns
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Oral Stage
• Sensory and Motor dysfunction
Weakened movements cause reduced
oral transit time, fodd may remain on
tongue and hard palate following
transit
 Epiglottis fail to invert over laryngeal
opening, limited elevation of the
hyoid, may be increased pooling of
food or liquid in the valleculae
 Difficulty initiating a reflexive swallow
may be due to a sensory deficit
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Deficit Patterns
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Pharyngeal Stage
• Sensory and Motor Dysfunction
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Slow velar elevation may result in nasal regurgitation
Reduced sensation of fauces, posterior tongue,
pharyngeal wall, soft palate may cause elevated
threshold for trigger of swallowing reflex
Reduced function of pharyngeal constrictors may
result in slowed pharyngeal transit time of bolus and
individual may reinitiate respiration
Weakened pharyngeal function may result in residue
left in the valleculae
Failure of the hyoid and thyroid to elevate may result
in loss of airway protection, food may fall into larynx
and be aspirated on breathing
Deficit Patterns
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Esophageal Stage
• GERD: acids from the stomach flow to
the esophagus and pharynx, may be
UES or LES problem or both
• Hiatal Hernia: LES may malfunction
allowing reflux into esophagus
• Congenital Malformation: stenosis, see
figure 9-4
Neurophysiological Terms
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Taste Buds (cells): chemoreceptors for gustation
Chemoreceptors: Neural receptors that respond to specific
chemical composition
Papillae: Prominences
Taste Pore: opening in lingual epithelium that houses taste cell
Microvilli: small, hairlike fibers projecting from the taste cell into
the taste pore
Mechanoreceptors: neural receptors designed to sense mechanical
forces
Glabrous: Hairless
Meissner’s Corpuscles: Superficial cutaneous mechanoreceptors
for minute movement
Merkel disk receptors: Superficial cutaneous mechanoreceptors for
light pressure
Pacinian Corpuscles: deep cutaneous mechanoreceptors for deep
pressure
Ruffini endings: deep cutaneous mechanoreceptors for tissue
stretch
Nociceptors: Pain sensors
Salivation: Production and release of saliva into to oral cavity
Neurophysiology
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Gustation
• Taste receptors (taste buds, taste cells)
• Class of sensors known as chemoreceptors
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Found within the epithelia of the with in papillae
or prominences
Taste pour: opening in lingual epithelium that
houses taste cell, permits isolation of the tasted
substance
Microvilli: small hairlike fibers projecting from the
taste cell into the taste pore, holds sample of food
in taste pore
Neurophysiology
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Gustation
• Taste mediated by 3 cranial nerves
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V!! mediates sense of taste from anterior 2/3 of the tongue,
sweet and sour sensations, and of palate. Sides transmit salt
and sour.
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IX mediates sense of taste, primarily of bitterness from
posterior 1/3 of tongue. Sides transmit salt and sour
X mediates sense of taste from epiglottis and esophagus
Umami: taste receptor which processes monosodium
glutamate.
Neurophysiology
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Gustation
• Taste VII CN
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Taste receptor
Geniculate ganglion
Medullary solitary tract (NST)
Rostral and lateral aspects of ST nucleus for gustation
Ventral posterior medial nucleus of thalamus
Information relayed ipsilaterally to the sensory cortex (post
central gyrus),anterior portion of the insula of the cerebral
cortex, and to the operculum overlying the insula.
Neurophysiology
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Gustation
• Taste IX CN
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Taste receptor
Petrosal ganglion
Medullary solitary tract (ST)
Rostral and lateral aspects of ST nucleus for gustation
Ventral posterior medial nucleus of thalamus
Information relayed ipsilaterally to the sensory cortex (post
central gyrus),anterior portion of the insula of the cerebral
cortex, and to the operculum overlying the insula.
Neurophysiology
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Gustation
• Taste X CN (epiglottal and esophageal)
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Taste receptor
Nodose ganglion
Rostral and lateral aspects of ST nucleus for gustation
Ventral posterior medial nucleus of thalamus
Information relayed ipsilaterally to the sensory cortex (post
central gyrus),anterior portion of the insula of the cerebral
cortex, and to the operculum overlying the insula.
Taste and small probably integrated in the insula
Fibers from the insula project to the limbic and motor
regions of the brainstem
Neurophysiology
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Gustation
• NTS projects to the motor cortex, specifically
area serving the tongue
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Tastes (sweet {carbohydrates}, protein {umami}
salt) will elicit salivation, ingestive responses
• Tongue protrusion to receive the food
• Release of insulin
• Mastication and deglutition
Neurophysiology
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Gustation
• NTS projects to the motor cortex, specifically
area serving the tongue
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Tastes, bitter and sour mat typify poison and elicit
a protective response
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Gagging
Coughing
Apnea
Salivation (encapsulates the material and protects the
oral cavity
Neurophysiology
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Gustation
• NTS projects to the motor cortex, specifically
area serving the tongue
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Taste can elicit motor responses that may or may
not be under volitional control
• Gag response
 Elevation of the larynx
 Clamping of the vocal folds
 Elevation of the velum
 Protrusion of the tongue
Neurophysiology
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Gustation
• NTS projects to the motor cortex, specifically
area serving the tongue
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Taste can elicit motor responses that may or may
not be under volitional control
• Coughing
 Tightly closing VF and supraglottic structures
 Compressing of abdomen and thorax
 Forcefully blowing VF apart
Neurophysiology
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Gustation
• Deglutition is made up of a complex set of
motor responses dictated by stimuli present
in the oral and pharyngeal spaces
Explain this
Neurophysiology
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Olfaction
• Olfactory chemoreceptors in nasal mucus membrane
• Sense of smell transmitted to olfactory bulb in
cranial space
• Then transmitted over olfactory tract to olfactory
region of the cortex, and from some to the thalamus
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Amygdala to hypothalamus
Anterior olfactory nucleus
Piriform cortex
Olfactory tubercle
Entorhinal cortex to hippocampus in the temporal lobe
Neurophysiology
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Olfaction
• Arrives at cerebral cortex through multiple
pathways and serves as a stimulus to
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Emotion and motivation (amygdala)
Physiological responses (hypothalamus)
Memory encoding (hippocampus)
Olfactory discrimination (orbitofrontal region of
the cerebral cortex)
Neurophysiology
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Tactile Sense
• In face and oral cavity, primarily mediated by V, but
IX and X are associated
• Mechanoreceptors are sensative to physical contact,
receptors vary according to type of touch
• Deep pressure has the potential to stimulate a larger
field and greater array of sensors than light
pressure, an issue that is important in treatment of
dysphagia
• Vibration sense is a subclass of tactile sense
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Best Frequency: The frequency if vibration at which a
sensor responds most effectively
Neurophysiology
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Thermal Receptors
• In face and oral cavity, primarily mediated by V, but
IX and X are associated
• Same as pain sensors, bare nerve endings
• Differentiate warm, hot, cool, cold: receptors are
tuned to particular temperatures
• Have a tonic, ongoing charge
• With high temperatures, heat sensors stop firing and
pain sensors fire
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Perception of pain can interfere with the ability to swallow
and swallowing responses
Neurophysiology
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Muscle stretch and Tension sense
• In face and oral cavity, primarily mediated by V, but
IX and X are associated
• Stretch receptors are found in oral muscles
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Masseter
Temporalis
Lateral and medial Pterygoid
Genioglossus
palatoglossus
• Muscle Spindle fibers (MSF)
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Return a muscle to its original position following passive
stretching (pulling down on relaxed jaw)
MSF designed to maintain a muscle at a preset length
MSF generally inhibited during active contraction
Neurophysiology
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Muscle stretch and Tension sense
• Muscle Tension
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Sensed by Golgi tendon organs (GTOs) within tendons and
facia
Muscle tone
• Perception of resistance to passive movement of a stretching
• regulated partially through interaction of muscle spindles and
GTOs
• High tone of spasticity due to inadequately inhibited response
from a muscle spindle sensor
• Low tone results from inadequate tonic stimulation either LMN
disease or cerebellar lesion
• Muscular rigidity results from a basal ganglia lesion and
demonstrates a cocontraction of agonist and antagonist
Neurophysiology
Salivation Response
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Not a sensory system but rather a motor response
Product of 3 glands: parotid, sublingual,
submandibular
• Stimulation of taste receptors on anterior 2/3 of tongue
mediated by VII via NS of dorsal pons (sublingual and
submandibular glands)
• Stimulation of taste receptors on posterior 1/3 of tongue
mediated by IX via inferior and superior salivatory nuclei
of the pons (parotid gland)
Neurophysiology
Salivation Response
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Parotid produces
Sublingual: produces mucus, a high-viscosity
protein rich secretion that helps in formation of
the bolus for food
Submandibular: produces serous (low viscosity,
thinner consistency) and mucus secretions,
lubricates the bolus
Parotid: produces serous saliva which helps the
bolus to be transported through the pharynx
Salivary response stimulated by sight, smell, and
taste of food