Introduction Definition Stages of deglutition Deglutition reflex Applied physiology

1. DEGLUTITION
Pandian M
Dept of Physiology
DYPMCKOP

2. Introduction
•Definition
•Stages of deglutition
•Deglutition reflex
•Applied physiology

3. Definition
•Deglutition or swallowing is the process by
which food moves from mouth into stomach.
It comprises three phases:
•Oral phase (voluntary),
•Pharyngeal phase (reflex or involuntary) and
•Oesophageal phase (reflex or involuntary).

4. ORAL STAGE or FIRST STAGE
• Oral stage of deglutition is a voluntary stage.
• In this stage, the bolus from mouth passes into
pharynx by means of series of actions.

5. Sequence of Events during Oral Stage
1. Bolus is placed over postero-dorsal surface of the tongue.
It is called the preparatory position
2. Anterior part of tongue is retracted and depressed.
3. Posterior part of tongue is elevated and retracted against
the hard palate.
This pushes the bolus backwards into the pharynx
4. Forceful contraction of tongue against the palate produces a
positive pressure in the posterior part of oral cavity.
This also pushes the food into pharynx

8. PHARYNGEAL STAGE or SECOND STAGE
• Pharyngeal stage is an involuntary stage.
• In this stage, the bolus is pushed from pharynx into the
esophagus.
• Pharynx is a common passage for food and air.
• It divides into larynx and esophagus. Larynx lies anteriorly
and continues as respiratory passage.
• Esophagus lies behind the larynx and continues as GI tract.
• Since pharynx communicates with mouth, nose, larynx and
esophagus, during this stage of deglutition.

9. • Bolus from the pharynx can enter into four paths:
1. Back into mouth
2. Upward into nasopharynx
3. Forward into larynx
4. Downward into esophagus.
• However, due to various coordinated movements, bolus is
made to enter only the esophagus.

10. • Entrance of bolus through other paths is prevented as
follows:
1. Back into Mouth
• Return of bolus back into the mouth is prevented by:
i. Position of tongue against the soft palate (roof of
the mouth)
ii. High intraoral pressure, developed by the
movement of tongue.

11. 2. Upward into Nasopharynx
• Movement of bolus into the nasopharynx from pharynx is
prevented by elevation of soft palate along with its extension
called uvula.
3. Forward into Larynx
• Movement of bolus into the larynx is prevented by the following
actions:
i. Approximation of the vocal cords
ii. Forward and upward movement of larynx
iii. Backward movement of epiglottis to seal the opening of
the larynx (glottis)

12. iv. All these movements arrest respiration for a few seconds.
It is called deglutition apnea.
Deglutition apnea
Apnea refers to temporary arrest of breathing.
Deglutition apnea or swallowing apnea is the arrest of
breathing during pharyngeal stage of deglutition.

13. 4. Entrance of Bolus into Esophagus
• As the other three paths are closed, the bolus has to pass only
through the esophagus.
This occurs by the combined effects of various factors:
i. Upward movement of larynx stretches the opening of
esophagus
ii. Simultaneously, upper 3 to 4 cm of esophagus relaxes.
This part of esophagus is formed by the cricopharyngeal
muscle and it is called upper esophageal sphincter or
pharyngoesophageal sphincter

14. iii. At the same time, peristaltic contractions start
in the pharynx due to the contraction of pharyngeal
muscles
iv. Elevation of larynx also lifts the glottis away
from the food passage.
All the factors mentioned above act together so
that, bolus moves easily into the esophagus.
The whole process takes place within 1 to 2 seconds
and this process is purely involuntary.

15. Esophageal stage or third stage
• It also known as an involuntary stage.
• In this stage, food (bolus) moves from esophagus to
the stomach.
• Esophagus forms the passage for movement of bolus
from pharynx to the stomach.
• Movements of esophagus are called peristaltic waves.

16. •Peristalsis means a wave of contraction,
followed by the wave of relaxation of muscle
fibers of GI tract,
•Which travel in aboral direction (away from
mouth).
•By this type of movement, the contents are
propelled down along the GI tract.

17. •When bolus reaches the esophagus, the peristaltic
waves are initiated.
•Usually, two types of peristaltic contractions are
produced in esophagus.
1. Primary peristaltic contractions
2. Secondary peristaltic contractions.

18. 1. Primary Peristaltic Contractions
• When bolus reaches the upper part of esophagus, the
peristalsis starts.
• It is initiated by swallowing & beings when food
passes into the oesophagus from the pharyngeal cavity
• It is coordinated by vagal fiber originating from the
swallowing centre within the medulla.

19. • Pressure developed during the primary peristaltic
contractions
• Its important to propel the bolus.
• Initially, the pressure becomes negative in the upper
part of esophagus.
• This is due to the stretching of the closed esophagus
by the elevation of larynx.
• But immediately, the pressure becomes positive and
increases up to 10 to 15 cm of H2O.

20. 2. Secondary Peristaltic Contractions
• If the primary peristaltic contractions are unable to
propel the bolus into the stomach,
• The secondary peristaltic contractions appear and push
the bolus into stomach.
• Secondary peristaltic contractions are induced by the
distention of upper esophagus by the bolus.
• After origin, these contractions pass down like the
primary contractions, producing a positive pressure.

21. Role of Esophageal Sphincter
• Upper oesophageal sphincter.
• Its a true sphincter formed by the cricopharyngeal
muscle.
• Its contracted tonically and serves to prevent the entry
of air into the oesophagus during normal respiration.
• Its tone is maintained by firing of vagal fibres from
the nucleus ambiguus.
• The neurotransmitter released by these fibres is Ach.

23. •Lower oesophageal sphincter.
• Cardiac sphincter or physiological sphincter
• Prevent regurgitation of gastric contents (food, gastric juice and
air) into the oesophagus.
• When the intragastric pressure is raised (e.g. after a heavy meal
or ingestion of carbonated drinks),
• The resistance of LES is overcome and air escapes into the mouth
(belching).
• The local hormone, gastrin, increases the tone of LES and helps
to keep the sphincter more tightly closed during digestion.

24. Components of swallowing reflex
• Receptors present around the opening of pharynx (especially
over tonsillar pillars) are stimulated
• When bolus moves from the mouth into the pharynx and
initiate the reflex activity.
• Afferent arc that carries impulses from the receptors to the
deglutition centre comprises the trigeminal,
glossopharyngeal and vagus nerve.

25. • Deglutition centre co-ordinating the reflex activity is
located in the medulla oblongata and lower pons (i.e.
in the nucleus of the tractus solitarius and the
nucleus ambiguus).
• Efferent arc, which initiates a series of muscular
contractions, reaches the pharyngeal musculature and
tongue through the 5th, 9th, 10th and 12th cranial
nerves.

27. APPLIED PHYSIOLOGY
1. Dysphagia
2. Abolition of deglutition reflex
3. Esophageal Achalasia or Achalasia Cardia
4. Gastroesophageal Reflux Disease (GERD)

28. 1. Dysphagia
Difficulty in swallowing.
Causes of dysphagia
i. Mechanical obstruction of esophagus due to
tumor, strictures, diverticular hernia (out pouching
of the wall), etc.
ii. Decreased movement of esophagus due to
neurological disorders such as parkinsonism
iii. Muscular disorders leading to difficulty in
swallowing during oral stage or esophageal stage.

29. 2. Abolition of deglutition reflex
• Abolition of deglutition reflex causes regurgitation of
food into the nose or aspiration into the larynx and
trachea.
• It may occur: When IX or X nerve is paralyzed in
lesions of medulla and
• When pharynx is anaesthetized with cocaine
(deglutition reflex is abolished temporarily).

30. 3. Esophageal Achalasia or Achalasia Cardia
•Its a neuromuscular disease,
•Characterized by accumulation of food
substances in the esophagus preventing normal
swallowing.
•It is due to the failure of lower esophageal
(cardiac) sphincter to relax during swallowing.
•The accumulated food substances cause
dilatation of esophagus.

31. Features of esophageal achalasia
i. Dysphagia
ii. Chest pain
iii. Weight loss
iv. Cough.

32. 4. Gastroesophageal Reflux Disease (GERD)
• GERD is a disorder characterized by regurgitation of
acidic gastric content through esophagus.
• The regurgitated gastric content flows into pharynx or
mouth.
• Regurgitation is due to the weakness or incompetence
(failure to constrict) of lower esophageal sphincter.

33. Features of GERD
i. Heart burn or pyrosis (painful burning sensation
in chest due to regurgitation of acidic gastric content
into esophagus)
ii. Esophagitis (inflammation of esophagus)
iii. Dysphagia
iv. Cough and change of voice
v. Esophageal ulcers or cancer (in chronic cases).

34. How to remember the Cranial nerves ????
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38. Referred :-
• Text book of Medical Physiology
• Guyton, 12th edition,
• Text book of Medical Physiology
• Indu khurana,
• Text book of Medical Physiology
• Vander’s
• Text book of Medical Physiology
• Sembulingam &
• LPR

39. THANK YOU . . .