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The Digestive System
Deglutition (Swallowing)
Deglutition (Swallowing)
 Involves the coordinated activity of the tongue,
soft palate, pharynx, esophagus and 22 separate
muscle groups
 Buccal phase – bolus is forced into the oropharynx
 Pharyngeal-esophageal phase – controlled by the
medulla and lower pons
 All routes except the one into the digestive tract are
sealed off
 Peristalsis moves food through the pharynx to the
esophagus
THEORY OF CONSTANT PROPORTION
1. Oral phase; the bolus is formed and
transported under voluntary control to the
pharynx;
2. Pharyngeal phase; following receipt of the
bolus, the pharynx is activated to propel the
food to the oesophagus;
3. Oesophageal phase; passage of bolus down
the oesophagus to the stomach by oesophageal
contraction
Physiology of Deglutition (Swallowing)

Moving bolus from
mouth to stomach
 Three phases
 Facilitated by saliva,

mucous secretions
Involves mouth,
pharynx, esophagus
1. Buccal phase
 Voluntary
 Occurs in the mouth
 Moves bolus to oropharynx
 Food is formed into a bolus
 The bolus is forced into the pharynx by the tongue
 Voluntary elevation and retraction of tongue
against the hard palate propels the bolus to the
pharynx
Physiology of Deglutition
2.Pharyngeal phase
 Involuntary
 It is very rapid (1 second) occur
reflexly {Swallowing reflex}
 Receptors in oropharynx




(tonsillar pillars)
Afferent : glossopharyngeal
nerves
Center: medulla oblongata
(Swallowing Center) and pons
Efferent :motor fibers of cranial
nerves V,IX,X,XII.
Response: series of reflexes to
prevent entry of food into air
passages:
Response: series of reflexes to prevent entry of food
into air passages:
1. Block mouth with tongue
2. Block nasopharynx with soft palate
3. Raise larynx to seal epiglottis, blocking airways
4. Relax upper esophageal sphincter
 Bolus is moved through pharynx into esophagus
.
 1-Elevation of soft palate closure of nasal cavity
 2-Approximation of palatopharyngeal folds
sagittal slit through which small food particles pass
and prevent passage of large particles
 3- Closure of glottis (opening of larynx) by
approximation of vocal cords& elevation of larynx and
folding of epiglottis.
 4-Inhibition of breathing (Swallowing apnea).
 5-Relaxation of pharyngeo-esophageal sphincter and
contraction of superior pharyngeal muscle –rapid
pharyngeal peristalsis –forces the food into relaxed
upper oesophagus.
Deglutition (Swallowing)
 Pharyngeal-esophageal phase
 Involuntary transport of the bolus
 All passageways except to the stomach are blocked
 Tongue blocks off the mouth
 Soft palate (uvula) blocks the nasopharynx
 Epiglottis blocks the larynx
 Peristalsis moves the bolus toward the stomach
 The cardioesophageal sphincter is opened when
food presses against it
Deglutition (Swallowing)
Figure 14.14
Deglutition (Swallowing)
Figure 22.13a-c
.
Physiology of Deglutition
3. Esophageal stage
 Upper esophageal sphincter
(UES) closes:
 pharyngeo-esophageal





junction is normally closed by
striated muscle tone to prevent
entry of inspired air into
stomach.
During swallowing the
sphincter relaxes reflexely and
then reclosed after swallowing.
Gastroesophageal
sphincter opens
Esophagus controls involuntary
peristaltic movement
Epiglottis reopens
Bolus moves from esophagus
to stomach
Esophagus
 Peristalsis
 Involuntary, rhythmic
contraction of
muscularis
 Controlled by
medullary centers
 A movement activity:
inner circular layer of
smooth muscle
contracts behind bolus
to push it forward;
outer longitudinal
muscle contracts to pull
esophagus wall up
 Upper esophageal




Esophagus
sphincter
Peristalsis
Lower esophageal
(cardiac/gastroesophageal)
sphincter
Sharp transition from
nonkertinized stratified
squamous epithelium to
simple columnar epithilium
Esophageal epithelium
resistant to abrasion but
not to acid and proteolytic
enzyme attack – acid
reflux disease
Esophageal phase
 Peristaltic contractions in body of esophagus
combined with simultaneous relaxation of the
lower esophageal sphincter propel the bolus
into the stomach.
CAUSES OF DYSPHAGIA
 Divided into two categories:
 Oropharyngeal dysphagia (OPD) Abnormalities
affecting the neuromuscular mechanisms controlling
movements of the tongue, pharynx, and UES
 Esophageal dysphagia (ED)
Abnormal affecting the esophagus itself
.
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.
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Deglutition (Swallowing)
Figure 22.13d, e
.
.
Oral Preparatory Phase
 tongue positions material on the teeth
 rotary lateral movement of the mandible and tongue
during mastication
 tongue moves the material back onto the teeth as the
mandible opens
 after cycle is repeated numerous times, a bolus is
formed
 during active chewing, the soft palate is not pulled
down and forward and premature spillage is common
and entirely normal