physiology

1. MASTICATION AND
DEGLUTITION
Aarya N Bharadwaj
I MDS

2. ● INTRODUCTION
● IMPORTANCE OF MASTICATION
● STRUCTURES INVOLVED IN MASTICATION
● JAW MOVEMENTS DURING MASTICATION
● MASTICATORY SEQUENCE
● CONTROL OF MASTICATION
● DEGLUTITION
● TYPES OF DEGLUTITION
CONTENTS

3. ● STRUCTURES INVOLVED IN DEGLUTITION
● STAGES OF DEGLUTITION
● FLUID INTAKE
● CONTROL OF DEGLUTITION
● APPLIED ASPECTS
● CONCLUSION
● REFERENCES

4. INTRODUCTION
MASTICATION is the process by which
food taken in the mouth is crushed into
small particles by the grinding action of
teeth.
DEGLUTITION is the process by which food
is passed into the stomach from the
oral cavity.

6. ● Mastication consists of the coordinated functions of various
parts of the oral cavity to prepare the food for swallowing and
digestion.
● Large food particles are broken down and mixed with
secretions of salivary glands to form a homogenized mass
called BOLUS.
● This wetting and homogenizing action aids in swallowing and
subsequent digestion.

7. ● Teeth, lips, cheeks, tongue, palate, gingiva and periodontium,
muscles of mastication and the temporomandibular joint, along
with the lubricating and enzymatic action of saliva are involved
in mastication.

8. The optimal number of chews usually ranges from 20-25.
The total number of swallows per day is approximately 600.
● 200- Eating and drinking
● 250- All through the day without food
● 50- Sleeping

9. The volume of a swallow varies-
● Child- 5 mL
● Adult Female-10-14 mL
● Adult Male- 15-20 mL

10. IMPORTANCE OF MASTICATION:
1. Large food particles can be digested, but they cause strong and
often painful contractions of the oesophageal musculature.
2. Particles that are small tend to disperse in the absence of
saliva, and this can make swallowing difficult.

11. 3. Breakdown of food into smaller particles increase the surface
area, resulting in effective digestion.
4. Mastication also helps in the removal of cellulose covering
certain food particles.
5. Saliva secretion is increased, and it lubricates the content of the
oral cavity, aiding in easier swallowing.

12. MUSCLES OF MASTICATION

13. MUSCLES OF MASTICATION
These are 4 pairs of muscles that are attached to the mandible and
are primarily responsible for elevating, protruding, retruding, or
causing the mandible to move laterally.
● They develop from the first pharyngeal
arch.
● Innervation- Trigeminal Nerve.
● Arterial supply- Maxillary Artery.

14. MUSCLE MASSETER TEMPORALIS
ORIGIN Lower border of the
Zygomatic arch
Temporal fossa;
Temporal fascia
INSERTION Lateral surface of the
ramus;
Coronoid process
Anterior border of
ramus;
Coronoid process
ACTIONS Elevation Elevation;
Retraction
NERVE
SUPPLY
Masseteric Nerve Anterior and posterior
deep temporal nerves

15. MUSCLE MEDIAL PTERYGOID LATERAL PTERYGOID
ORIGIN Maxillary tuberosity;
Medial surface of
lateral pterygoid
plate
Greater wing of
sphenoid;
Lateral surface of
lateral pterygoid plate
INSERTION Medial surface of
mandibular angle
and ramus
Pterygoid fovea;
TMJ
ACTIONS Elevation; Depression;
Retraction;
Lateral movements
NERVE
SUPPLY
Nerve to Medial
Pterygoid
Nerve to Lateral
Pterygoid

16. ACCESSORY MUSCLES OF
MASTICATION
Anterior belly of Digastric
Geniohyoid
Mylohyoid
Buccinator

17. MUSCLE ORIGIN INSERTION ACTION NERVE
SUPPLY
DIGASTRIC Digastric
fossa of the
mandible
Intermediate
tendon
Elevates
hyoid bone;
Depresses
mandible
Nerve to
mylohyoid
MYLOHYOID Mylohyoid
line on the
mandible
Median raphae;
Body of the
hyoid bone
Elevates
hyoid, floor of
the mouth;
Depresses
mandible
Nerve to
mylohyoid

18. BUCCINATOR Pterygomandibular
raphae;
Maxilla and mandible
opposite molars
Blends in
with the
muscles
around
the mouth
Flattens cheek against
gums and teeth;
Prevents accumulation
of food in the vestibule
Buccal
nerve
GENIOHYOID Inferior genial
tubercle of mandible
Body of
hyoid
bone
Elevates hyoid;
Depresses mandible
when hyoid s fixed
C1 through
hypogloss
al nerve

19. UNIQUE FEATURES OF MASTICATORY MUSCLES
● Have shorter contraction times than most other body muscles.
● Incorporate more of muscle spindles to monitor their activity.
● Do not have golgi tendon organs to monitor tension.
● Elevators are predominantly white fibrous which perform fast
twitching.

20. ● Do not fatigue easily.
● Psychological stress increases the activity of elevator muscles.
● Occlusal interferences can cause a hypertonic synchronous
muscle activity.
● Closing movement also determined by the height of the teeth.

21. MUSCLE ACTIVITY
EMG recordings of jaw muscles during mastication exhibit an
asynchronous pattern of activity during contraction with a wide
variation in time of onset, peak activity and rate of decline.
The pattern of activity is determined by factors such as-
● Species
● Type of food
● Rate of food breakdown

22. ● Muscles involved in the opening movement of mandible are
active during the opening.
● Muscles that are responsible for the closing of the mandible
start showing movement only when the jaw begin to close and
teeth begin chewing.

23. TEMPOROMANDIBULAR JOINT
● Temporomandibular Joint is a synovial joint that articulates
between the mandible and the temporal
bone.
● It connects the mandible to the skull and
regulates its movement to perform
important functions like speech and
mastication.
● It is a bicondylar joint, located at either
end of the mandible.

24. COMPONENTS OF THE TMJ
BONE/HARD TISSUE
COMPONENTS:
1. Mandibular condyles
2. Glenoid fossa of the temporal bone
3. Articular eminences
SOFT TISSUE COMPONENTS:
1. Articular capsule
2. Articular disc
3. Ligaments
4. Muscles

25. MANDIBULAR CONDYLES-
● They are ovoid, convex processes that are broad laterally and
narrow medially.
● They are connected to the body of the mandible by a narrow neck.
● The anterior surface has a
shallow depression-
Lateral Pterygoid Fovea.

26. GLENOID FOSSA-
● It is the articular surface of the temporal bone, which is
situated on the inferior surface of the squamous part of the
temporal bone.
● It is thin in the articular fossa and
thickens in the posterior region
of the articular eminence.

27. ARTICULAR EMINENCES-
● It is the part of the temporal bone that binds the mandibular
fossa anteriorly and forms the anterior root of the zygomatic
process.

28. ARTICULAR CAPSULE-
● It is a thin sleeve of dense, cartilaginous tissue enclosing the joint
cavity.
● Attachments: Below- Neck of the condyle
Above- Glenoid fossa, articular eminence
● Anterolateral part is thickened to form the Temporomandibular
Ligament.
● Posterior part blends into the articular disc.

29. ARTICULAR DISC-
● This ia a roughly oval, firm, thick plate of dense,fibrous cartilage,
located between the condyle and the articulating surface of the
temporal bone.
● It divides the joint cavity into-
superior and inferior compartments.
● Functions as shock absorber and
stress distributor.

30. ARTICULAR LIGAMENTS-
1 TEMPOROMANDIBULAR
LIGAMENT
Lateral aspect of the
articular eminence-
Posterior part of the
condylar neck.
● Prevents displacement in
posterior and inferior
directions.
● Prevent lateral
displacement of one joint
and medial displacement of
the other

31. 2. SPHENOMANDIBULAR
LIGAMENT
Spine of the sphenoid- Lingula
of the mandible
● Limits distension of
the mandible in an
inferior direction.
3. STYLOMANDIBULAR
LIGAMENT
Apex of the styloid process-
Angle of the mandible (posterior
border)
● Limits the
excessive opening
of the mouth.
4. PTERYGOMANDIBULAR
RAPHAE
Hamulus of medial pterygoid
plate- Posterior end of
mylohyoid line.

32. MUSCLES-
LATERAL PTERYGOID:
Function- Pulls the coronoid process of the mandible anteriorly
forcing the condylar process out of the mandibular fossa along the
articular eminence to protrude the mandible.

33. TONGUE
● The tongue plays an essential role in controlling the movement
of food and formation of bolus.
● The food has to be positioned by the tongue
in conjunction with the buccinator muscles
between the occlusal surfaces of the teeth.
● The tongue transports solid and liquid food
within the oral cavity.

34. SALIVA
● Saliva contain ZYMOGEN granules, which contain salivary
enzymes that are discharged from the acinar cells into ducts.
● 1500 mL of saliva is secreted everyday.
● pH of resting gland is slightly <7; can go upto 8 during active
secretions.
PAROTID GLAND SEROUS
SUBMANDIBULAR
GLAND
MIXED
SUBLINGUAL GLAND MUCOUS

35. SALIVA contains-
● Digestive enzymes like lingual lipase and salivary α amylase.
● Mucins and glycoproteins- lubricate food, bind bacteria, protect
the oral mucosa.
● Immunoglobulins, specifically secretory IgA
● Lysozymes that attack bacterial walls
● Lactoferrin- binds iron and is a bacteriostatic
● Proline rich proteins- protect the enamel and bind toxic tannins

36. ● The digestive functions of saliva include moistening food and
helping to create a food bolus. This lubricative function of
saliva allows the food bolus to be passed easily from the
mouth into the esophagus.
● Enzyme amylase, also called ptyalin, is capable of breaking
down starch into simpler sugars. About 30% starch digestion
takes place in the mouth cavity.
● Salivary lipase initiates fat digestion.

37. JAW MOVEMENTS
● Mastication is characterized by large vertical movements of the
lower jaw, accompanied by some transverse movements of the
mandible, and protrusion and retrusion of the tongue.
● Although new borns feed by suckling, tongue and mandibular
movements generally begin in utero.
● While chewing, the jaw moves rhythmically, and the opening
and closing occurs in a series of cyclical movements- ‘Chewing
Cycle’.

38. Preparatory
Phase
Food
Contact
Phase
Crushing
Phase
Phase of
Tooth
Contact
Grinding
Phase
Centric
Relation
Tongue positions food in the oral cavity.
Mandible deviates towards chewing side.
Sensory receptors are
triggered due to food
contact.
Begins with high
velocity; slows down
as food get crushed.
Mandible
returns to single
terminal point
Movements
guided by
occlusal tables
All reflex muscular adjustments for
tooth contact made
CHEWING
CYCLE

39. SEQUENCE OF FOOD INTAKE

40. ● Consists of many chewing cycles and extends from ingestion to
swallowing.
● Can be divided into three consecutive periods-
1. PREPARATORY- Initial period where food is transported to the
posterior teeth
2. REDUCTION- Intermediate period where food is broken down
3. PRE SWALLOWING- Final period where bolus is formed for
swallowing.
MASTICATORY SEQUENCE

41. CONTROL OF MASTICATION
● Motor and sensory nuclei contained in the brainstem play a
pivotal role in the control of mastication.
● These movements require the integrated activity of muscles
controlled by the Trigeminal, Facial and Hypoglossal nerves,
and other motor nuclei in the brainstem.

42. Reflex inhibition of
contraction the
muscles of
mastication
Raises the jaw to
cause apposition of
teeth and
compression of bolus
Activation of
stretch reflex of
muscles
Contraction of
the muscles
Lower jaw
drop
CHEWING REFLEX

43. ● The mastication process is controlled by a ‘Central Pattern
Generator’ and masticatory muscles exhibit specific reflex
patterns.
● Types of muscle reflexes of the masticatory apparatus-
1. Jaw- closing reflex
2. Jaw- opening reflex
3. Unloading reflex

44. JAW- OPENING REFLEX-
● This reflex is initiated by mechanical stimulation of the
periodontal ligament and mucosal mechanoreceptors.
● The result is excitation of jaw- opening muscles and inhibition of
jaw- closing muscles.
● It is a polysynaptic reflex.
● There are numerous reflex pathways involved in this reflex.

45. JAW- CLOSING/ JAW- JERK REFLEX-
● The reflex activity of the jaw moving the teeth into occlusion.
● It is a monosynaptic reflex occuring due to stretching of muscle
spindles in the masseter, bringing the teeth into occlusion.

46. UNLOADING REFLEX-
● It is a protective reflex that occurs during a heavy occlusal load.
● Mastication is stopped due to reflex inhibition of elevators and
reflex excitement of depressors.
● Receptors in the periodontal ligament protect teeth from
damage.

47. MASTICATORY FORCE
● Maximum biting force that can be applied to teeth varies
between individuals.
● Anterior teeth- 10-15 kg
● Posterior teeth - 50 kg
● Biting force can be measured-
Gnathodynamometer.

48. DEGLUTITION
● Deglutition is a reflex activity consisting of muscle contractions
and relaxations that help push ingested food and saliva from
the mouth into the stomach.
● Though it is initiated voluntarily, most of this process is
involuntary or reflexive.

49. ● Swallowing is initiated by the voluntary action of collecting oral
contents on the tongue and propelling them backward into the
pharynx.
● This starts a wave of involuntary contraction in pharyngeal
muscles that pushes the material into the oesophagus.
● Inhibition of respiration and glottic closure are a part of this
reflex response.

50. ● TYPES-
A.Infantile swallow
B. Mature/ Adult swallow

51. VISCERAL SWALLOW
● Also called ‘Infantile swallow’, this swallow pattern exists at birth.
● It is characterized by the forward movement of the tongue tip.
● Infants swallow by suckling. This reflex is well developed and
takes care of the infant’s feeding and emotional needs.

52. ● Jaws remain apart with the tongue interposed between the
gum pads.
● Lower jaw is held and stabilized primarily by the contraction of
facial muscles and the interposed tongue.
● The tongue is so closely placed next to the lips and tunnelled
so as to allow the milk to flow directly into the pharynx and
oesophagus.
● The swallow is guided largely by the sensory interchange
between the lips and tongue.

53. SOMATIC SWALLOW
● Maturing of swallow occurs with the addition of semisolid and
solid food to the diet.
● It is characterized by -
1. Relaxation of lips and placement of tongue tip against the palate
and behind upper incisors.
2. Increase in intraoral volume and change in tongue posture.
3. Stabilization of mandible by contraction of muscles of mastication.

54. COMPONENTS OF DEGLUTITION-
● Passage of bolus from oral cavity to stomach
● Protection of airway
● Inhibition of air entry into the stomach

55. THEORIES OF DEGLUTITION
1. In 1880, the theory was proposed that fluids and semi fluids
are propelled directly into the stomach by the contraction of the
tongue and the mylohyoid muscles effecting a syringe like
action to pressure the liquid downwards. The muscles of the
pharynx proper came into play only for propulsion of solid food
substances.

56. 2. THEORY OF NEGATIVE PRESSURE- Another concept of the
mechanism of deglutition was advanced as the results of the use
of fluoroscopy. A radiolucent area in the laryngopharyngeal cavity
was observed just prior to the propulsion of the bolus in to the
pharynx. The radiolucent area disappeared immediately to provide
space for the bolus. This concept gave rise to the presence of
negative pressure within the laryngopharyngeal cavity that pulled
the bolus in by suction.

57. 3. The concept that the process of deglutition is performed
successively by contraction of the oral, pharyngeal, and
oesophageal muscles has been confirmed by the
roentgenographic studies by Bosma. He called the theory “motion
in anticipation of the approaching bolus”. He was impressed by a
particular position or posture assumed by the upper part of the
pharynx and the consecutive elevation of the larynx and
laryngopharyngeal area an instant prior to penetration by the bolus.

58. 4. THEORY OF INTEGRAL FUNCTION -
● This theory is based on myometric & electromyographic
studies & considers the act of swallowing as a total dynamic
process.
● All theorists agree that the pharynx is endowed with extreme
rapidity and therefore all the structures involved in deglutition
must be flexible and elastic.
● It is the most accepted theory.

59. MUSCLES OF THE SOFT PALATE
● The soft palate forms the posterior end of the roof of the
mouth.
● Five pairs of muscles-
1. Palatoglossus
2. Palatopharyngeus
3. Musculus Uvulae
4. Levator veli palatini
5. Tensor veli palatini

60. PALATO-
GLOSSUS
PALATO-
PHARYNGEUS
MUSCULUS UVULAE
ORIGIN Palatine
aponeurosis
Palatine
aponeurosis;
Posterior part
of hard palate
Palatine
aponeurosis;
Post nasal
spine
INSERTION Lateral border
of the tongue
Pharyngeal
wall;
Thyroid
cartilage
Uvula
ACTIONS Pulls up the
tongue
Pulls up the
pharynx
Pulls up the
uvula
NERVE
SUPPLY
Glossopharyng
eal via Vagus
Glossopharyng
eal via Vagus
Glossopharyng
eal via Vagus

61. LEVATOR VELI
PALATINI
TENSOR VELI PALATINI
ORIGIN Inferior aspect
of auditory tube
Lateral aspect of auditory tube;
Adjoining part of sphenoid bone
INSERTION Upper part of
palatine
aponeurosis
Forms the palatine aponeurosis.
Posterior border of hard palate;
Inferior surface of palate at the
palatine crest
ACTIONS Elevates soft
palate;
Opens auditory
tube
Tightens soft palate;
Opens auditory tube
NERVE
SUPPLY
Glossopharyng
eal via Vagus
Mandibular Nerve

62. BLOOD SUPPLY-
● ARTERIAL SUPPLY-
1. Greater palatine artery
2. Ascending palatine artery
3. Palatine artery
● VENOUS DRAINAGE- Is by the corresponding veins into the
pterygoid and tonsillar venous plexus.

63. PHARYNX
● The pharynx is a cone-shaped passageway leading from the oral
and nasal cavities in the head to the oesophagus and larynx.
● The pharynx serves both respiratory
and digestive functions.
● Length- 12 cms
● Width- 3.5 cm and narrows down

64. ● Thick fibres of muscle and connective tissue attach the
pharynx to the base of the skull and surrounding structures.
● Both circular and longitudinal muscles occur in the walls of the
pharynx;
1. Circular muscles form constrictions that help push food to the
oesophagus and prevent air from being swallowed, while
2. Longitudinal fibres lift the walls of the pharynx during
swallowing.

65. PARTS OF THE PHARYNX
The pharynx can be divided into three anatomical parts-
1. NASOPHARYNX
2. OROPHARYNX
3. LARYNGOPHARYNX

66. MUSCLES OF THE PHARYNX
Two groups of muscles are associated with the pharynx-
Muscles that ELEVATE
and DILATE the pharynx-
1. Palatopharyngeus
2. Stylopharyngeus
3. Salpingopharyngeus
Muscles that CONSTRICT
the pharynx-
1. Superior Constrictor
2. Middle Constrictor
3. Inferior Constrictor

67. ORIGIN INSERTION
SUPERIOR
CONSTRICTOR
Pterygoid hamulus;
Pterygomandibular
raphae;
Medial surface of
mandible;
Side of posterior part
of tongue
Median
raphae
attached to
occipital
bone
MIDDLE
CONSTRICTOR
Stylohyoid ligament;
Lesser cornua of hyoid
bone
Median
Raphae
INFERIOR
CONSTRICTOR
Cricoid and thyroid
cartilages of larynx
Median
Raphae
PHARYNGEAL CONSTRICTORS:

68. ORIGIN INSERTION
PALATOPHARYNGEUS Soft and
hard palate
Thyroid
Cartilage
STYLOPHARYNGEUS Styloid
process of
temporal
bone
Thyroid
Cartilage
SALPINGOPHARYNGEUS Cartilage
around the
inferior
portion of the
auditory tube
Thyroid
Cartilage
PHARYNGEAL ELEVATORS:

70. BLOOD SUPPLY-
● Arterial Supply-
1. Ascending pharyngeal branch of External Carotid Artery
2. Ascending palatine and tonsillar branches of Facial Artery
3. Dorsal Lingual branches of Lingual Artery
4. Greater palatine, pterygoid and pharyngeal branches of
Maxillary Artery
● Venous Drainage- Plexus on the posterolateral aspect of
pharynx- Internal Jugular and facial veins
NERVE SUPPLY- Pharyngeal Plexus
1. Pharyngeal branch of Vagus nerve with fibres of Cranial
Accessory nerve

71. OESOPHAGUS
● The oesophagus is a fibromuscular tube, about 25 centimetres
long in adults through which food passes, aided by peristaltic
contractions, from the pharynx to the stomach.
● It travels behind the trachea and heart, passes through the
diaphragm and empties into the uppermost region of the
stomach.

72. STAGES OF DEGLUTITION
Deglutition can be divided into three phases-
1. Oral stage - Voluntary phase, which initiates the swallowing
process.
2. Pharyngeal stage – Involuntary phase, constitutes the passage
of food through the pharynx into the oesophagus.
3. Oesophageal Stage –Involuntary phase, which promotes the
passage of food from pharynx into the stomach.

74. PREPARATORY PHASE-
● Formation of food bolus occurs during this phase.
● Food bolus is a round/oval mass of food formed in the mouth
after thorough chewing.
● It is formed as a preparatory event
for swallowing.

75. ● Tongue– The action of its intrinsic muscles alters its shape. The
extrinsic muscles changes its position within the oral cavity
thereby helping in chewing the food.
● Occlusal action of the lips - Seal & prevent the bolus from
dribbling out of the oral cavity.
● Buccinator muscle – Maintains the bolus in the oral cavity
proper.
● Bolus accumulates on the oro-pharyngeal surface of tongue due
to repeated cycles of upward & downward movement of the
tongue.

76. ORAL PHASE
● Also called ‘Buccal phase’, this phase begins once the bolus is
positioned on the dorsum of the tongue.
● Lips close and the incisors come together.
● Anterior two-thirds of the tongue elevate
against the maxillary alveolar ridge
and the anterior hard palate, propelling
the bolus towards the pharynx.

77. ● Nasopharynx is shut by the upward movement of soft palate
and forward movement of posterior pharyngeal wall.
● This prevents regurgitation of food through the nose.
● This is a voluntary phase and respiration is stopped for a while
during this phase.

78. PHARYNGEAL PHASE
● At the beginning of this phase, the posterior part of the tongue
makes a rapid piston- like movement to propel the bolus through
the oropharynx into the hypopharynx.
● Pharyngeal constrictors move upward and
forward; begin propelling the bolus through
the pharynx by sequential contractions.
● Upper oesophageal sphincter opens, and
bolus enters the oesophagus.

79. ● The laryngeal vestibule closes due to movement of the
epiglottis.
● It moves from an upright position to a horizontal position.
Muscle contractions further cause the tip of the epiglottis to
rotate over the laryngeal vestibule.
● It directs the bolus into the pyriform sinus, and around the
opening of the airwar into the oesophagus.

80. Mechanisms to prevent aspiration of the bolus into the airway-
● Respiration is inhibited.
● Elevation of larynx and upper oesophageal sphincter shortens the
distance that the bolus must travel and the duration of its
presence at the entry of the airway.
● Intrinsic muscles of glottis forcefully approximate the vocal cords.
● Trapping of any residual bolus is at a lower level than the
laryngeal vestibule, making aspiration unlikely.

81. ROLE OF EPIGLOTTIS:
● Movement of epiglottis occurs in two stages- from a horizontal
to a vertical position.
● Upper third of the epiglottis moves
to a slightly lower level to cover
the narrowed laryngeal inlet.

82. ● Bolus, during the course of the swallow impinges on the
epiglottis and gets diverted to lateral channels-
● Solid- behind the epiglottis into the postcricoid area.
● Liquids- get split by epiglottis and pass via pyriform fossae.

83. OESOPHAGEAL PHASE
● After the food is placed in the upper end of oesophagus, the
upper oesophageal sphincter contracts.
● A peristaltic ring contraction is formed
behind the bolus, which is then swept into
the oesophagus at a speed of 4 cm/s.
● Aided by gravity.

84. ● Lower oesophageal sphincter opens to allow the bolus into the
stomach.
● The musculature of this sphincter, unlike the rest, is tonically
active, but relaxes on swallowing,
● This tonicity prevents reflux of gastric contents into the
oesophagus.
● Intrinsic and extrinsic sphincter exerts a pinch-cock like effect
on the oesophagus, and oblique fibres of the stomach create a
flap valve to close this junction.

85. Lower oesophageal sphincter is under neural control:
● Intrinsic sphincter- fibres from Vagus nerve
● Extrinsic sphincter- Phrenic nerves
Both the sphincters act together to
permit orderly flow of food into the
stomach and prevents reflux of
gastric contents into the oesophagus.

86. FLUID INTAKE
● It is possible to ingest fluids without any oral activity.
● If the head is tipped back to allow the oral cavity and
oesophagus to present a straight path, fluid can be poured
down this pathway.

87. Accumulation of fluid in the anterior part of the oral cavity, with the tongue
hollowed at the tip but raised posteriorly.
Tip of the tongue raises to touch the palate behind the upper incisors..
Muscles of the tongue contract progressively to bring it back along the palate.
Posterior part of the tongue drops down.
Pharyngeal phase that follows is similar to the swallowing of bolus;
Fluids can pass down the oesophagus under the influence of gravity; even
then, contraction of the upper oesophageal sphincter and initiation of peristaltic
waves occur.

88. CONTROL OF DEGLUTITION
● Swallowing can be initiated either voluntarily or by stimulation
of various areas in the oropharynx.
● The reflex response is triggered by afferent impulses in cranial
nerves V, IX, X.
● Impulses are integrated in nucleus of tractus solitarius and
nucleus ambiguus.
● Efferent fibres pass to pharyngeal musculature through cranial
nerves V, VII, IX

89. ● Preparatory and oral phases are voluntary, whereas the pharyngeal
and oesophageal phases are involuntary.
● Control of swallowing is the property of a precisely interconnected
set of neurons.
● Swallowing motor sequence and motility of smooth muscles of the
oesophagus depends on the swallowing centre.
● Swallowing centre is not a discrete anatomical entity, but consists
of brainstem sensory and motor nuclei interconnected by a
neuronal network.

90. Swallowing centre comprises of three components:
1. Sensory input that terminates in nucleus of tractus solitarius
and trigeminal sensory nucleus that are involved in the
initiation of swallowing
2. Motor output deriving from neurons within nucleus ambiguus,
facial, trigeminal and hypoglossal nuclei, and motor neurons in
cervical spinal cord.
3. An interneuronal network that programs the entire sequence of
a swallow through excitatory and inhibitory connections.

91. APPLIED ASPECTS
● Trismus- Restricted mouth opening that occurs due to spasm
of masticatory muscles.
● TMJ disorders
● Parafunctional habits
● Malocclusions
● Lesions in cranial nerves IX, X
● Digestive problems in edentulous patients.

92. ● Dysphagia- Difficulty in swallowing can occur when the above
structures are affected by any infection, inflammation.
● Nasal regurgitation- This can occur in patients with palatal
clefts or paralysis of soft palate.
● Motor disorders of the oesophagus- GERD, Achalasia
● Aeroplasia- Trapping of air in the oesophagus
● Aspiration pneumonitis- Occurs due to inhalation of gastric
contents.

93. Since around 50 pairs of muscles are involved in swallowing,
dysphagia can occur due to various conditions like-
1. Acid reflux and GERD
2. Epiglottitis
3. Goiter, Thyroid nodule
4. Esophageal cancer
5. Oesophagitis , herpes oesophagitis
6. Recurrent herpes simplex labialis
7. Infectious mononucleosis

94. CONCLUSION
● The inter–relationship and intimate interdependence between
mastication and deglutition, along with respiration and
phonation are from a neurophysiologic point of view
overwhelmingly complex and extremely fascinating.
● The smooth performance of these vertical function requires a
complex integration of the cranial somatic innervation in
coordination with the A.N.S.

95. ● Integration of physiology and the kinetics of mastication is
required for any occluso-dontic procedure. Interpretation of
muscular action during mastication, incision, trituration, and intra-
dental functional guidance is essential.
● Deglutition also allows a functional impression to be made without
excessive pressure in case of prosthetic needs. The borders will
conform to the physiological limits and hence will allow for perfect
harmony between the dentures and the oral tissues.

96. REFERENCES
● Krishna Garg.B. D. Chaurasia’s Human Anatomy, Volume 3. 5th
edition. CBS Publishers and Distributors.2010. p148-60,205-23.
● Brand RW, Isselhard DE. Anatomy of Orofacial structures. 6th
edition. Mosby Inc, USA. p161-80,188-95.
● Venkatesh D, Sudhaker HH. Basics of Medical Physiology. 2nd
edition. Wolters-Kluwer India.

97. ● Nallaswamy D. Textbook of Prosthodontics. Jaypee Brothers
Medical Publishers (P) Ltd; 2004. p118.
● www.googleimages.com

98. ● Ganong WF. Review of Medical Physiology. 22nd edition.
McGraw-Hill Companies, Singapore. p488-91.
● Ramya R, Rajkumar K. Textbook of Oral Anatomy, Histology,
Physiology and Tooth Morphology. Wolters Kluwer (India), New
Delhi; 2016. p39-44,368-77.
● Kharbanda OP. Orthodontics- Diagnosis and Management of
Malocclusion and Dentofacial Deformities. 2nd
edition,Gurgaon: Elsevier, India; 2013. p133

99. THANK YOU