DEGLUTITION REFLEX
Though the beginning of swallowing is a voluntary act, later it becomes involuntary and is carried out by a reflex action called deglutition reflex. It occurs during the pharyngeal and esophageal stages.
Stimulus
When the bolus enters
the oropharyngeal region, the receptors present in this region are stimulated.
Afferent Fibers
Afferent impulses from
the oropharyngeal
receptors pass via the glossopharyngeal nerve fibers to the
deglutition center.
Center
Deglutition center is
at the floor of the fourth ventricle in medulla oblongata of brain.
Efferent Fibers
Impulses from
deglutition center travel through glossopharyngeal and vagus nerves
(parasympathetic
motor fibers) and
reach soft palate, pharynx and esophagus. The glossopharyngeal nerve is
concerned
with pharyngeal stage
of swallowing. The vagus nerve is concerned with esophageal stage.
Response
The reflex causes upward
movement of soft palate, to close nasopharynx and upward movement of larynx, to
close respiratory passage so that bolus enters the esophagus. Now the peristalsis
occurs in esophagus, pushing the bolus into stomach.
1. Dysphagia
Dysphagia means
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.
2. Esophageal Achalasia or Achalasia Cardia
Esophageal achalasia
or achalasia cardia is 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 accumu lated food substances cause dilatation of
esophagus.
Features of
esophageal achalasia
i. Dysphagia
ii. Chest pain
iii. Weight loss
iv. Cough.
3. 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.
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).
1. Gastric Dumping Syndrome
Gastric dumping syndrome
or rapid gastric emptying is the condition characterized by series of upper
abdominal symptoms. It is due to the rapid or quick dumping of undigested food
from stomach into the jejunum. It occurs in patients following partial gastrectomy (removal
of stomach) or gastroenterostomy
(gastric bypass surgery). The rapid gastric emptying may begin immediately
after taking meals (early
dumping) or about few hours after taking meals (late dumping).
Causes
i. Gastric surgery.
ii. Zollinger-Ellison
syndrome (rare disorder due to
severe peptic ulcer
and gastrin-secreting tumor in pancreas).
Symptoms of early
dumping
i. Nausea and vomiting
ii. Bloating (increase
in abdominal volume with feeling of abdominal fullness and tightness)
iii. Diarrhea
iv. Sweating and
weakness
v. Fatigue and
dizziness
vi. Fainting and palpitations
(sensation of heart beat).
Symptoms of late
dumping
i. Hypoglycemia
ii. Sweating and
weakness
iii. Dizziness.
2. Gastroparesis
Gastroparesis is a
chronic disorder characterized by delayed gastric emptying. It usually occurs
as a
secondary disorder,
precipitated by a primary cause.
Causes
i. Diabetes mellitus
ii. Postsurgical
complications
iii. Motility disorder
iv. Gastric infection
v. Metabolic and
endocrine disorder
vi. Decrease in
myenteric ganglia (rare).
Symptoms
i. Early satiety (feeling
full with small quantity of food)
ii. Nausea
iii. Vomiting
iv. Bloating
v. Upper abdominal discomfort.
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