Anatomy and Neurophysiology of Swallowing

Anatomical and physiological substrate in the normal process of swallowing,
Neuro-muscular control of swallowing process

1. The normal physiology of
feeding
Mr. Hemarja Nayaka.S
Assistant Prof. in Speech Sciences

2. Normal stages of feeding
•Integrated interdependent group
of complex feeding behaviors
emerging from interacting cranial
nerves of the brainstem and
governed by neural regulatory
mechanism in the medulla ,
•as well as in sensorimotorand
limbic cortical systems.

3. transferring or
transporting of the bolus
from oral and pharyngeal
passages to the
esophagus
(oropharyngealtransfer
or transport phase),&
transporting of the bolus
through the esophagus to
the stomach (esophageal
transport phase).
The process of
swallowing
includes the
conscious effort to
ingest food and the
largely subconscious
(reflex) efforts of
preparing the bolus
to be swallowed
(preparatory phase),

4. 2
3
1
Stages of
swallowing
Oral transport
phases
Pharyngeal phase
Oral preparatory
Esophageal phase
4

5. RoleofMusclesandMotorNerves
MusclesofPhysiologicImportancein
differentphases
RoleofAfferentNerves
CentralNervousSystemControl

6. Oral preparatory phase
Oral transfer phase
Oral phase….

7. Ingestion of a
bolus usually
requires active
lowering of the
mandible,
opening of the
lips, and
depression of the
tongue actions
that increase the
size of the oral
cavity to
accommodate the
ingested bolus.

8. During ingestion by
sucking, such as with a
straw, the lips remain
sealed around the delivery
vessel and the exit to the
back of the oral cavity is
closed by the tongue and
soft palate.

9. •Lowering of the mandible
along with depression and
retraction of the tongue
are accompanied by
bracing of the cheeks and
mouth floor.
•These actions generate a
subatmospheric pressure
within the oral cavity that
facilitates flow of fluids
into the oral cavity. Such
suction may also serve to
drive entry of saliva into
the oral cavity from the
salivary glands.

10. Mastication is
necessary for
rendering solid
ingested boluses into
a size, shape, and
consistency that is
amenable to
transport. This action
requires complex
variations in the
force and velocity of
mandibular
movement, holding
and grinding solids
with the teeth.
During this process the cheeks and
tongue function to position the solid over
the grinding surfaces. The tongue also
helps reduce softer or dissolvable solids
by mashing them against the bony
structures bounding the oral cavity and
mixing them with liquid elements of the
ingested bolus.

11. Secreted saliva also
facilitates dissolving
and lubricating solid
boluses and is the
major stimulus for the
basal swallow rate
between periods of
ingestion.
Secreted saliva also
facilitates dissolving
and lubricating solid
boluses and is the
major stimulus for the
basal swallow rate
between periods of
ingestion.

12. Oral transfer phase….

13. At the start of the oral transfer phase the
superior perimeter of the tongue is pressed
against the hard palate, sealing the bolus
from the anterior oral cavity. Especially
with large liquid boluses, the posterior
aspect of the tongue and soft palate are
closed together to prevent premature spill
of the bolus into the pharynx.
In a rapid sequence, the tongue
presses against the hard palate,
generating a pressure wave
directed posteriorlythat
propels the bolus into the
oropharynx.

14. The force of this tongue action
can be volitionally modified.
Concurrent with this action,
the soft palate elevates, while
the cheeks, floor of mouth, and
jaw are braced.
The oral phase can be considered
completed when the bolus tail enters
the oropharynx, at which point the
posterior dorsum of the tongue
remains sealed against the soft palate
to prevent retrograde escape of bolus
back into the oral cavity.

15. The larynx and
pharynx are at rest
during the oral
preparatory phase
of swallowing.
The airway is open
and nasal
breathing
continues.

16. Role of Muscles
and Motor Nerves

17. Several muscle groups
participate in the oral
phase of swallowing .All
of these are striated
muscles using
acetylcholine for
neurotransmission via
nicotinic receptors.
The oral phase is
voluntary, and is
controlled by the
cerebral cortex and
corticobulbartracts of
the brain.

18. The mandibularbranch of
trigeminal nerve (cranial nerve
V) innervates the principle
muscles for chewing
behaviors .
The facial nerve (cranial
Nerve VII) innervates lower
facial muscles attached to
maxillae and mandible of the
skull
Hypoglossal nerve (Cranial nerves
XII) innervates the tongue intrinsic
muscles masses that have different
effects on shape ,contour , and
function of the tongue.
Motor nerve
control

21. The facial muscles are also
activated during some
swallows to develop an
anterior seal of the lips.
Theintrinsicmusclesofthe
tonguearesuppliedbyCN
XII.Theyhavenobony
attachments. Because
muscle tissue is
incompressible,themuscles
ofthetonguefunctionasa
hydrostat,whereinchanges
inshapedonotresultina
changeinvolume.
The extrinsic muscles of the tongue have their origin
on various bony structures and insert into the tongue
and their innervationis by CN XII. Actions of the
extrinsic muscles elevate, depress, protrude, and
retract the tongue.
Muscles

22. The suprahyoidmuscles
overall act to raise the hyoid
bone and larynx, whereas the
infrahyoidmuscles have the
opposite action. The
suprahyoidmuscles are
supplied by motor neurons
located in the trigeminal and
facial nuclei in the pons,
Thepalatalmusclegroupis
innervatedfrommotor
neuronsresidinginthe
trigeminalnucleusor
nucleusambiguous.
These muscles act during the oral phase of
deglutition to stiffen the soft palate, lower the soft
palate to prevent premature bolus spill into the
pharynx, or elevate the soft palate to open the oral
cavity posteriorly.
Muscles of
oral phase

24. Mandible Opening
The lateral
pterygoid, anterior belly of
the digastric, and to some
degree geniohyoid,
mylohyoid, and platysma
assist with opening the
mandible. The initial
process of depression begins
with contraction of the first
two. These muscles are
fairly weak compared with
those that assist in jaw
closure.
Sealing Muscles
Sealing muscles
include the orbicularis
oris, levatorlabii
superiorisand depressor
labiiinferioris, levatorand
depressor angularis, and
mentalismuscles.
Contraction of these
muscles causes elevation,
depression, protrusion,
closure, and pursing
activities of the lips.

25. Bolus Manipulation
Some muscles that
control and manipulate the
bolus include the following:
The buccinatormuscle
controls bolus formation by
flattening and tensing the
cheek whereas both the
intrinsic and extrinsic
tongue musculature
manipulate and control the
bolus.
Mandible Closing
The masseter,
temporalis, and medial
pterygoidmuscles are
powerful muscles that
assist in mandibular
closure, mastication, and
grinding.

27. Role of Afferent
Nerves

28. Afferent sensory neurons important in the oral phase of
swallowing travel in CNs V, VII, IX, and XI.
Sensory input is critical to the oral phase of swallowing,
because assessment of the chemical and physical
properties of the bolus at this point allows ready expulsion
of boluses with noxious properties.
Sensory feedback is also required during bolus preparation and
transport to allow appropriate positioning of oral structures;
modulate the strength, velocity, and timing of muscle
contractions; and determine the position and readiness of the
bolus for transport.
Some sensory pathways subserve protective reflexes, such as
the gag reflex. Finally, stimulation of certain sensory receptive
fields acts to initiate, or facilitate the initiation of, deglutition.

30. Taste sensation is conveyed by
special visceral afferent fibers
from the anterior two thirds of
the tongue (CN VII), the
posterior third of the tongue
(IX), and epiglottis (X), with
these fibers terminating in the
nucleus tractus solitarius
(NTS).

32. These fibers terminate in the mesencephalic (stretch,
proprioception), spinal (pain, temperature), and main sensory
(touch, pressure) nuclei of CN V.
Taste information is conveyed rostrally from the NTS to the
thalamus, insula, and hypothalamus.
Sensations of light touch, temperature, pressure, pain, muscle
stretch, and proprioception for most of the oral cavity and the
anterior two thirds of the tongue are conveyed from fibers that
ascend in CN V.

33. General somatic
afferent innervationof
the posterior third of
the tongue and the
faucialpillars ascends
through CN IX to the
NTS. Some neurons
that synapse in the
NTS also send axons
rostrallyto the pons
and cortex.
The importance of sensory
input for the initiation of the
oral transport phase of
deglutition is self-evident by
noting the maximal
swallowing frequency that
can be obtained while
drinking a glass of water at
the fastest possible rate
compared to the lower
sustainable deglutitiverate
observed with dry swallows.

35. Central Nervous
System Control

36. Spontaneous, swallowing
occurs about once per
minute in the awake state, is
greatly reduced during
sleep, and increases during
emotional stress. Damage to
different areas of the cortex
can result in difficulties
with mastication and the
initiation of swallowing.
These observations
underline the
importance of cortical
and cognitive input to
the oral phase of
swallowing.

38. In humans, functional
imaging studies have
identified multiple regions
above the brainstem that are
active during mastication,
including the cortex
(sensorimotor, prefrontal,
supplementary motor area,
insula), thalamus, and
cerebellum.
Subjects with a
chewing side
preference show
dominant activity in
the contralateral
sensorimotor cortex
during tongue
movement.
Masticatory activities
are inhibited by
induction of
swallowing.

39. AGENDA
Multiple cortical areas
including the
sensorimotor, insular,
prefrontal, anterior
cingulate, parieto-
occipital cortex, along
with the amygdala,
thalamus, basal ganglia,
and cerebellum have
been shown to be
activated during
voluntary swallowing.

40. Physiology of
the Pharyngeal
Phase of
Swallowing
AGENDA

41. •Anatomically, the
pharynx can be
divided into the
•nasopharynx(above
soft palate),
•oropharynx(from soft
palate to
pharyngoepiglottic
fold),
•hypopharynx
(pharyngoepiglottic
fold to
cricopharyngeus
muscle).

42. The swallow reflex involves high cortical centers, brain stem
centers, and cranial nerves V (trigeminal), VII (facial), IX
(glossopharyngeal), X (vagus) and XII (hypoglossal).
Thisistheshortest,but
mostcomplexphase.
This phase is
involuntaryandis
triggeredbycontactof
theboluswiththe
tonsillarpillarsand
pharyngealwall.
Ittakesplaceinless
thanonesecond.

43. There are 29
muscle pairs
which are
involved in this
phase of
swallowing.
The pharyngeal
phase descriptively
is that period from
when the swallowed
bolus first enters the
pharyngeal cavity
until the bolus tail
exits the UES.

44. During the
pharyngeal phase,
three of the potential
exits (upper airway,
mouth, and lower
airway) must close
while the bolus is
rapidly propelled into
the fourth
(esophagus).

45. The time from bolus entrance to
bolus exit from the pharynx is
slightly less than 1 second.
This time is longer for larger
boluses, due to earlier entrance
into the pharynx from the start
of the swallow. The forceful
backward thrust of the tongue
accelerates the bolus head
rapidly. With larger bolus
volumes, velocity at the level of
the UES may exceed 30 cm/sec,
whereas velocities of solid
particles may approach 40
cm/sec in the supraglottic
region .

46. During the pharyngeal phase of swallowing
the tongue maintains a position against the
palate to seal the oropharynx.

47. A number of physiological activities occur as a result of pharyngeal triggering,A number of physiological activities occur as a result of pharyngeal triggering,
A number of physiological activities occur as
a result of pharyngeal triggering,

48. Age of lesion onset
Nature of neurological insults
(2) elevation and anterior movement of the
hyoid and larynx;
(1) elevation and retraction of the velum and
complete closure of the velopharyngeal port to
prevent material from entering the nasal cavity
(3) closure of the larynx at all three sphincters –the
true vocal folds, the laryngeal entrance , and
epiglottis –to prevent material from entering the
airway;

49. Age of lesion onset
Nature of neurological insults
(6) progressive top to bottom contraction in
the pharyngeal constrictors
(5) ramping of the base of the tongue to deliver the
bolus to the pharynx followed by tongue base
retraction to contact the anteriorly bulging
posterior pharyngeal wall;
(4) opening of the cricopharyngeal sphincter
to allow material to pass from the pharynx
into the esophagus

50. Velopharyngeal
closure
v
AGENDA

51. Velopharyngeal
closure varies
somewhat from person
to person and may
involve some elements
of elevation and
retraction of the soft
palate, inward
movement of the
posterior and or lateral
pharyngeal walls, and
an anteriorly bulging
adenoid pad.
Velopharyngeal closure
enables the buildup of
pressure in the pharynx.
Functional swallowing is
possible without
velopharyngeal closure if
all other physiologic
aspects of the pharyngeal
swallow are normal,
particularly the tongue base
and pharyngeal wall
movement and contact.

53. Elevation and
Anterior Movement
of the Hyoid and
Larynx
AGENDA

54. During the swallow the larynx
and hyoid bone elevate and
move anteriorlyby the pull of
the floor of mouth muscles
(i.e. the anterior belly of
digastric, mylohyoid,
geniohyoid, and the laryngeal
elevator, the thyrohyoid).
In young men, the hyoid
elevates approximately 2 cm
(Jacob et al. 1989). The
elevation contributes to
closure of the airway
entrance, and the forward
movement contributes to
opening of the upper
esophageal sphincter.

55. Example text
Go ahead and
replace it with
your own text.
AGENDA
Closure of the
Larynx

56. closure of the larynx as
beginning at the level
of the vocal folds and
progressing upward to
the laryngeal vestibule.
During closure of the airway
at the vestibule, there is a
downward, forward, and
inward rocking movement of
the arytenoids cartilages,
which narrows the laryngeal
opening

57. At the same time, the
larynx is elevated and
pulled forward. This
elevation thickens the
base of epiglottis,
assisting with closure
of the laryngeal
vestibule

58. In normal adults the airway
entrance is closed for
approximately one third to
two thirds of a second
during single swallows.
During sequential cup
drinking, the airway may be
closed 5 seconds or more

59. Cricopharyngeal
Opening
AGENDA

60. Cricopharyngealopening
occurs by a complex series
of actions
First, tension in the
cricopharyngeal
muscular portion of the
sphincter is released.
Approximately 0.1
second later, laryngeal
anterior superior motion
is seen to begin to open
the sphincter;

61. the sphincter is yanked open by the
motion of the larynx resulting from the
upward and forward pull of the floor of
the mouth muscles.
The leading edge of the
bolus reaches the sphincter as
it opens, and the pressure
within the bolus widens the
opening (Jacob et al. 1989).
As the bolus passes through
the sphincter, the larynx
lowers and the
cricopharyngeusmuscle
returns to some level of
contraction.

62. Example text
Go ahead and
replace it with
your own text.
AGENDA
Tongue Base
and
Pharyngeal
Wall Action

63. As the pharyngeal swallow
triggers, the tongue base
assumes a ramp shape,
directing the food into the
pharynx. Then, tongue base
retraction and pharyngeal wall
contraction occur when the
bolus tail reaches the tongue
base level.
The tongue base and pharyngeal
walls should make complete
contact during the swallow
(Kahrilaset al. 1992). As the
two structures move toward each
other, pharyngeal pressure
builds. When the two structures
make contact, the pharyngeal
wall contraction continues
progressively down the pharynx
to the upper esophageal
sphincter, where esophageal
peristalsis takes over bolus
propulsion.

65. The triggering of the pharyngeal swallow

66. If the oral tongue
propels the bolus
posteriorlyand no
pharyngeal swallow is
triggered, the bolus is
likely to be propelled by
the tongue into the
pharynx, where it may
come to rest in the
valleculaeor pyriform
sinuses
No pharyngeal swallow actions will
occur until the pharyngeal swallow
triggers, so the bolus may rest in the
valleculaeuntil the pharyngeal swallow
is triggered. Or, depending on
consistency, the food may drain from
the valleculae, down the aryepiglottic
folds and into the pyriformsinuses, or
may fall into the airway where it may
or may not be expectorated, depending
upon the patient’s sensitivity in the
trachea and larynx
It is important to remember that a swallow comprised of velar,
pharyngeal, tongue base, and laryngeal activity occurs only as a
result of the triggering of the pharyngeal swallow.

67. Watch out…1

69. Watch out…2

71. Role of Muscles and Motor
Nerves

72. All of the muscles
involved in the
pharyngeal phase of
swallowing are striated
muscle and use
acetylcholine as their
neuromuscular
transmitter via
nicotinic receptors.

73. Thecellbodiesofthe
motorneuronssupplying
thesemusclesresidein
brainstemnucleilocated
inthepons(trigeminal)
andmedulla(nucleus
ambiguous,hypoglossal)
orintheanteriorhornof
thecervicalspinalcord
(C1-2).Axonsfromthese
motorneuronstravelvia
cranialnervesV,IXtoXII

74. Pharyngeal
Phase Muscles
Action of the
palatopharyngeus
muscles to approximate
the palatopharyngeal
folds may help seal the
oral cavity. In addition,
the back of the tongue is
compressed forcefully
against the back of the
oropharynx, clearing the
bolus into the
hypopharynx. The tongue
remains pressed against
the back of the
oropharynx usually until
the bolus tail exits the
hypopharynx
The intrinsic and extrinsic
muscles of the tongue
continue the action
initiated in the oral phase.
As the tail of the bolus
clears the oral cavity, the
dorsum of the tongue
remains compressed
against the hard and soft
palate, thus preventing
retrograde bolus escape
back into the oral cavity.

75. Pharyngeal
Phase Muscles
The muscles of the
pharynx can be divided
into two functional
groups, based on their
action. Contraction of the
longitudinal group
(palatopharyngeus,
stylopharyngeus,
salpingopharyngeus)
elevates and shortens the
pharynx. The action of
the stylopharyngeus also
widens the pharynx and
opposes anterior
movement of the
posterior pharynx. The
actions of these muscles
elevate the larynx as well.
The muscles in the palatal
group act to tense and
elevate the soft palate to
seal the entrance from the
oropharynx to the
hypopharynx. The upper
portion of the superior
pharyngeal constrictor also
contracts to close the
pharynx medially as part
of the nasopharyngeal seal.
The soft palate elevation is
maintained until the bolus
tail exits the hypopharynx,
after which the soft palate
usually returns to a rest
position

76. Pharyngeal
Phase Muscles
Action of the
palatopharyngeus
muscles to approximate
the palatopharyngeal
folds may help seal the
oral cavity. In addition,
the back of the tongue is
compressed forcefully
against the back of the
oropharynx, clearing the
bolus into the
hypopharynx. The tongue
remains pressed against
the back of the
oropharynx usually until
the bolus tail exits the
hypopharynx
Muscles in the circular
group (superior, middle,
inferior constrictors) have
partial overlap at their
borders. Contraction
proceeds in an aboral
direction to clear the
trailing portion of the
bolus into the esophagus.
All of the pharyngeal
muscles have their motor
neurons located in the
nucleus ambiguous and are
innervated via the
pharyngeal plexus, except
for the stylopharyngeus
(CN IX).

77. Pharyngeal Phase
Muscles
All of the intrinsic
laryngeal muscles
involved in deglutition
have their motor neurons
in the nucleus
ambiguous, and the axons
pass through the inferior
laryngeal branch of the
recurrent laryngeal nerve
(CN X).
The intrinsic muscles of the
larynx function to close the
glottis and supraglottic space,
approximating the arytenoids
cartilages to the base of the
epiglottis.Vocal cord closure
occurs before the closure of
the laryngeal vestibule by the
downward movement of the
epiglottis. Downward
movement of the epiglottis to
a horizontal position depends
on forces transmitted via the
ligament between the
epiglottis and hyoid as the
hyoid moves anteriorly and
superiorly.

78. Afferent system

80. Activation of receptive fields supplied
byCNIX and X can trigger reflexive, or
pharyngeal, swallows. Receptive fields
supplied by the superior laryngeal nerve have
the lowest threshold for initiating a swallow.
Sensory feedback modulates muscular function
during the pharyngeal phase of swallow. This is
manifest by alterations in timing and magnitude
of neuromuscular events. Both bolus volume
and consistency can modulate activity
Afferent
system

81. CNS control

82. TheSPGconveniently lies within theNTS
which is the primary sensory relay for the
sensory information from the pharynx and
also receives cortical input.
Neurons of theSPG send projections to the
lower motor neurons for the oral and
pharyngeal muscles.
The activity of theSPGis coordinated with other
medullaryreflexes. For example, it is difficult to elicit a
swallow when the cortical masticatorycenters are
stimulated. The timing of deglutition in response to
pharyngeal water stimulation can be volitionally
modified.
CNS
Control

83. The incidence and relative timing of activation of various
deglutitivemuscles varies between individuals and
between swallows in the same individual.

84. Physiology of the
Esophageal stage

85. Upper
esophageal
sphincter
Lower
esophageal
sphincter

86. Was provided by comparisons of the
sensitivity and specificity of the 3
compensation methods.
The specificity was ~ 7% less than that
achieved by the standard Stacked ABR
(92%).
Bolus transport in the thoracic esophagus is quite different
from that of the pharynx, because it is true peristalsis
regulated by the autonomic nervous system. Once the food
bolus enters the esophagus passing the UES, a peristalsis
wave carries the bolus down to stomach through the LES.
The lower esophageal sphincter is also tensioned at rest to
prevent regurgitation from the stomach. It relaxes during a
swallow and allows the bolus passage to the stomach. The
cervical esophagus (upper one third) is mainly composed of
striated muscle but thoracic esophagus (lower two thirds) is
smooth muscle.

87. The peristaltic wave
consists of two main
parts, an initial wave of
relaxation that
accommodates the
bolus, followed by a
wave of contraction that
propels it. Gravity
assists peristalsis in
upright position.

88. Was provided by comparisons of the
sensitivity and specificity of the 3
compensation methods.
The specificity was ~ 7% less than that
achieved by the standard Stacked ABR
(92%).
Normal esophageal transit time varies from 8 to 20
seconds (Dodds et al.,1973)
Esophageal transit times can be measured from the point
where the bolus enters the esophagus at the cricopharyngeal
juncture or UES until it passes into the stomach at the
gastroesophageal juncture or LES.
Once the bolus has entered into the esophagus, its rate of
progression slows to 3-4 cm/s. It is propelled by a primary
peristaltic wave beginning in the upper one third of the
esophagus and progressing to the stomach. A secondary
wave in mid esophagus can be developed in response to
local distention.

90. UES
The UES, which is closed at rest, releases during
swallowing as the larynx elevates. Relaxation of the
sphincter precedes opening by approximately one-tenth of
a second
The duration and diameter of sphincter opening is
influenced by bolus size and viscosity which implies that
sphincter response is not stereotypic but is responsive to
sensory feedback.
The sphincter opens by forces of traction on the
anterior wall exerted by contraction of the suprahyoid
and infrahyoid muscles.

91. UES functions
prevention of esophageal distention during normal breathing
(Palmer, 1976) and protection of the airway against aspiration
following an episode of gastroesophagealreflux
Afferent pathways from adjacent structures also
participate in reflexes that modulate UES tone.
Afferent sensory neurons from the UES have their cell
bodies in the nodose ganglion and synapse in the NTS.
Provides feedback on the state of tension in the muscle.

92. Althoughmuchofthe
actionoftheUESduring
deglutition appears
stereotyped,itsfunction
canbemodifiedby
sensoryfeedbackfromthe
swallowedbolus.
With larger boluses, the
UES pressure relaxes earlier
and longer and the UES
lumen opens longer and
wider. The duration of UES
opening during deglutition
can also be modified
volitionally.

93. Neurologiccontrolof
peristalsisin the
esophagusisrelatedto
bothcentralandperipheral
mechanisms.

94. In the striated portion of the
esophagus, peristalsis is under
control of the central nervous
system. This portion of the
esophagus receives only
somatic excitatory innervation
originating from lower motor
neurons of the nucleus
ambiguous located in the
brainstem with preganglionic
fibers traveling in the vagus
nerve.
Peristalsis is activated
when the swallowing
center stimulates the
nucleus ambiguous to
sequentially fire
neurons in a cranial-
caudal sequence

95. Therefore,althoughinitiation
ofaprimaryperistalticwave
requirescentralnervous
systeminput,sequencingof
thewaveisafunctionof
intrinsicneuralpathways
withintheesophagealmuscle
(i.e.peripheralcoordination). Direct stimulation of the
vagusnerve will result in a
peristaltic sequence.
However, the vagusis not
necessary for secondary
peristalsis. Peristalsis may
occur independently of the
central nervous system.

96. LES
2
The LES, which is closed at rest, relaxes during
deglutition to allow passage of esophageal contents
into the stomach
1
The LES functions as a major determinate of
gastroesophageal competence and provides a
barrier against reflux of gastric contents into the
esophagus

97. Stimulation of the
hypopharynxexerts a
powerful inhibitory effect
on the esophagus and
theLES. Small amounts of
fluids in the pharynx can
attenuate ongoing
peristaltic waves in the
esophagus and result in
isolated relaxation of
theLESwhen there is no
peristalsis. This reflex is
mediated by long
vagovagalpathways.
stimulation of the
hypopharynxwith water
results in vocal cord
closure, a reflex mediated
byCNIX that can serve to
prevent aspiration from
refluxed liquids or boluses
that fail to clear the
esophagus during
deglutition.
Pharyngoesophageal and
Laryngeal Reflexes

98. Pharynx and Upper
Esophageal Sphincter
During Belching
Pharynx During
Vomiting

99. Neuro chemical
aspects of swallowing .

100. Glutamate
excitatory neurotransmitter
high concentrations in the region of
the nucleus solitarius (NS)
mediate rapid-onset, short-duration
afferent sensory signals important in
reflexively initiated deglutition.

101. Gamma-amino butyric acid (GABA)
inhibitory neurotransmitter
GABA neurons produce a tonic
inhibition of deglutitive neurons in the
central pattern generator
GABA has also been implicated in the
inhibition of respiration and other
vegetative reflexes produced by muscle
afferent fibers involved in deglutition,
and by inhibitory hypothalamic inputs.

102. Acetylcholine
cholinergic neurons have been
shown to participate in the vagal motor
efferents for swallowing arising in the
region of the brainstem central pattern
generator, and may be particularly active
during the esophageal phase of
swallowing.
critical role as the major transmitter at
the neuromuscular junction, post-
ganglionic transmission in the
parasympathetic nervous system,
preganglionic transmission in both
sympathetic and parasympathetic
systems.

103. Dopamine and nor epinephrine
appear to have a predominantly facilitatory effect on
central control centers for swallowing.
Dopamineplays a role in deglutition.
Patients with Parkinson’s disease, in which there is a
loss of dopaminergic neurons, frequently complain of
dysphagia.
Benzodiazepines, such as nitrazepam and
clonazepam, which are GABA agonists, are known to
depress swallowing activity, supporting a role for
GABA-mediated inhibitory neurotransmission.

104. Opioidpeptides
somatostatin, oxytocinand
vasopressin are also present and
active in central deglutitive
mechanisms
Although their precise roles remain
to be defined, their abundance and
variable effects attest to a high degree
of complexity in the brainstem
regulatory mechanisms subserving
deglutition and respiration.

105. Age related changes of
Swallowing Skills

106. Prenatal Swallowing
and Sucking
Infants and children
In population with
aging…

107. •The development of
feeding and swallowing
involves a highly
complex set of
interactions that begin
in embryologic and
fetal periods and
continue through
infancy and early
childhood
Prenatal Swallowing
and Sucking

108. In utero swallowing is important for the regulation of amniotic
fluid volume and composition, recirculation of solutes from
the fetal environment, and the maturation of the fetal
gastrointestinal tract.
The pharyngeal swallow, one of the first motor responses in
the pharynx, has been observed between 10 and 12 weeks'
gestation.
Recent studies have demonstrated swallowing in most fetuses
by 15 weeks' gestation and consistent swallowing by 22 to 24
weeks' gestation.
True suckling begins around the 18th to 24th week and is
characterized by a distinct backward and forward movement of
the tongue.

109. The frequency of suckling motions can be
altered by taste. Taste buds are evident at 7
weeks' gestation
By 12 weeks’ gestation, distinctively mature
receptors are noted. Self oral-facial stimulation
usually precedes suckling and swallowing.
Tongue cupping is seen by 28 weeks' gestation.
Backward movement appears more pronounced
than forward movement. Tongue protrusion does
not extend beyond the border of the lips.

110. Premature infant patterns differ from those of full-term infants.
Lack of regular swallowing by the fetus should lead one to
suspect problems that may be related primarily to the preterm
infant or primarily to the mother.
Decreased rates of fetal suckling are associated with digestive
tract obstruction or neurologic damage.
Intrauterine growth retardation may be a manifestation of
neurologic damage
Oral feeding that requires suckling, swallowing, and breathing
coordination is the most complex sensorimotor process the
newborn infant undertakes

111. Pre natal
swallowing
Swallowing function Gestational age
(weeks)
Pharyngeal swallow 10–14
True suckling 18–24
Tongue cupping 28
Sustain nutrition totally orally34–37

112. Normal Feeding
Abnormal feeding

113. In population with
aging…

114. Aging Summary of current findings
Oral phase Slowinganddecreasedefficiencyoftonguemovement
Reducedstrengthofmasticatorymuscles
Increasedoraltransittime
Boluspostionedmoreposteriorlyintheoralcavity
Decreasedsuctionpressurethroughstrawwithrepetitiveswallows,stamina
decreases
Pharyngeal phaseSwallowresponsetriggeredlowinpharynx
Largerbolusvolumesrequiredtotriggerpharyngealswallow
Rateofspontaneousswallowislessfrequent
Delayedanteriorhyoidmovement
Reducedanteriorexcursionofhyolaryngealcomplex
Increaseddurationofvelarelevation
Increasedpharyngealtransittime
Moreswallowsrequiredtoclearoralandpharyngealcavities;increasedpost
swallowresidue
Increasedfrequencyofcoughingafterswallow
Reducedpharyngeal,laryngealsensitivity
UES Decreasedamplitudeofperistalsis
DelayedUESopening/relaxation,relatedtoincreasedoraltransittimes
ReducedUESflexibility

115. Co ordination of respiration and swallowing
Cortical structures also play an important role in facilitating
and modulating the coordination of breathing and swallowing.
Neural control centers responsible for coordination of
breathing and swallowing are contained in the dorsomedial
and ventrolateral medullary regions of the brainstem.
Breathing and swallowing processes are closely interrelated in
their central control and are highly coordinated. Many
muscles and structures have dual roles in respiration and
swallowing.

116. Recap………..!!!

117. References
Koichiro Matsuo,& Jeffrey B. Palmer, Anatomy and
Physiology of Feeding and Swallowing –Normal and
Abnormal Phys Med Rehabil Clin N Am. 2008 November ;
19(4): 691–707. doi:10.1016/j.pmr.2008.06.001.
Murray & Carrau (2006) Clinical management of swallowing
disorders , second edition , plural publishing ,Inc .2006
Deglutition and its disorders-Anatomy, Physiology, Clinical
diagnosis and Management” by Perlman and delrieu ( Ed).
“Neuroscientific principles of swallowing and dysphagia” by
Miller A.J. Singular publishing group. San Diego.

118. Joan C. Arvedson (2006) Swallowing and feeding in infants
and young children GI Motility online(2006)
doi:10.1038/gimo17
Benson T. Massey (2006 ) Physiology of oral cavity, pharynx
and upper esophageal sphincter GI Motility
online(2006)doi:10.1038/gimo2 Published 16 May 2006
Kim Corbin lewis ,Julie M.Liss , Kellie L.S. (2005) clinical
anatomy and physiology of swallow mechanism , Thomson
Delmer Learning, the star logo, USA.

119. Thank you !!