Deglutition, stages , nervous control, process, clinical significance for MBBS students.

1. Deglutition
Dr Anand More
Department of Physiology
D.Y.Patil Medical College, Kolhapur

2. Deglutition
 The process by which swallowing of food is
helped
 It also includes reflex action.
 Helped by movement of pharynx
 Closure of epiglottis to close larynx
 Upward movement of palate

3. Stages of Deglutition
 Oral stage
 Pharyngeal stage
 Oesophageal stage

6. Oral stage
 Orval stage is voluntary stage of deglutition.
 When food is ready for swallowing, bolus
formed is put over the dorsum of the tongue.
Tongue pressed against the palate and is
moved backward, moving the bolus from
mouth to pharynx

7. Pharyngeal stage
 When bolus moves from mouth to pharynx,
receptors around opening of pharynx are
stimulated, impulses from these areas pass to
the brain stem deglutition centre to initiate
series of muscular contraction.
 Soft palate moves upwards and close
posterior nasal openings to prevent food into
the nose.

8.  Palatopharyngeal folds on either side of
pharynx approximate to make a slit like
opening so only properly masticated food can
pass through.(Selective action)
 Vocal cords of larynx strongly approximate,
larynx is pulled upward and anteriorly by neck
muscles. Epiglottis swings backward to close
laryngeal opening. This prevents entry of food
in trachea.
 Upward movement of larynx enlarges opening
of oesophagus. Pharyngo-oesophageal
sphincter relaxes.

9.  At the same time entire muscular wall of the
pharynx contracts from superior to inferior
part, originating a fast peristaltic wave which
also continues in oesophagus. This wave
pushes the food from pharynx to oesophagus.

11. Nervous control of Pharyngeal
stage
 Pharyngeal stage of swallowing is a reflex. It
is initiated by tactile stimulation in the area of
opening of pharynx (especially tonsillar pillar
which are very sensitive)
 Impulses are carried from these areas
through 5th and 9th cranial nerves to medulla
(deglutition centre). Efferent impulses from the
centre pass through 5th, 9th, 10th and 12th
cranial nerves to cause different sequential
events in pharyngeal phase

12.  Entire pharyngeal stage of swallowing lasts
for 1-2 seconds. Pharynx is a common
pathway for food and air. Therefore during
pharyngeal stage airway above (nasal cavity)
and below (trachea) is closed to prevent entry
of food into respiratory passage. In addition,
swallowing centre inhibits respiratory centre of
the medulla to halt the respiration during any
time in its cycle. The momentary stoppage of
respiration is known as deglutition apnoea.

14. Oesophageal stage
 Oesophageal stage conducts food from
oesophagus to stomach by movements as
follows.
 Primary Peristalsis- It is simply continuation
of peristaltic wave initiated in pharynx. It takes
8-10 seconds to carry food to stomach. But in
upright posture food passes in the stomach
earlier 5-8 sec because of gravity.

15.  Secondary Peristalsis- If primary peristaltic
wave fails to carry all the food to the stomach,
secondary peristaltic wave is initiated in
oesophagus due to distension of oesophagus
with food. These waves continue till all the
food entered is emptied into the stomach.
These waves are produced due to intrinsic
neural circuits in the wall and partly due to
vagal reflex.

16. Types of muscle from
oesophagus
 Musculature of pharynx and upper one third
of oesophagus is formed of skeletal muscle
whereas lower two third of oesophagus is
formed of smooth muscles.
 Inner layer is circular muscle and outer layer
is longitudinal muscle.

17. Clinical Significance
 Abolition of deglutition reflex - Causes
regurgitation of food into nose or aspiration
into larynx or trachea
 Aerophagia - Unavoidable swallowing of air
along with food bolus and liquids. Usually
occurs in nervous individuals. Partly the air
absorbed is regurgitated in oral cavity
(belching) majority passes as flatus.

18.  Dysphagia - Difficulty in swallowing due to
any cause.
 Cardiac achalasia - It’s a neuromuscular
disorder of lower two third of oesophagus
characterized by absence of peristalsis and
failure of LES to relax
 Gastroesophageal reflux disease - It is
condition in which incompetence of LES
causes reflux of acidic gastric contents in
oesophagus and causes heartburn.

19. Summary
 Stages of Deglutition
 Oral stage
 Pharyngeal stage
 Nervous control of Pharyngeal stage
 Oesophageal stage
 Types of muscle from oesophagus
 Clinical Significance

20. References
Textbook of Medical Physiology – Guyton And
Hall 13th Edition
Textbook of Physiology – A K Jain 6th Edition
Medical Physiology For Undergraduate
Students – Indu Khurana
Net Source for pictures & etc.