Swallowing

Question 1

What is the structure of the alimentary canal?

Answer 1

Mucosa
Submucosa
Muscularis
Serosa

Question 2

What are the components of the mucosa?

Answer 2

Epithelium
Lamina propria (areolar connective tissue + lymphatic tissue)
Muscularis mucosae (smooth muscle)

Question 3

What are the components of the submucosa?

Answer 3

Areolar connective tissue
Blood and lymphatic vessels
Neurons - submucosal plexus (Meissner plexus)

Question 4

What are the components of the muscularis?

Answer 4

Smooth muscle (Circular and longitudinal): Enables peristalsis and segmental contraction
Neurons – myenteric plexus (Auerbach plexus)

Question 5

What are the components of the serosa?

Answer 5

Connective tissue & epithelium

Question 6

What are the muscles of chewing innervated by?

Answer 6

Mandibular branch ofcranial nerve V

Question 7

What are the stages of swallowing?

Answer 7

Stage 1: Oral (buccal) phase
Stage 2: Pharyngeal phase
Stage 3: Esophageal phase

Question 8

What is the oral phase?

Answer 8

Voluntary stage
Food is squeezed or rolled posteriorly into the pharynx by the tongue

Once initiated, it cannot be stopped

Question 9

What is the pharyngeal phase?

Answer 9

Involuntary phase
Food entering the pharynx stimulates epithelial swallowing receptor areas, passing impulses to the brain stem which initiates automatic pharyngeal muscle contractions

Question 10

What are the stages of the pharyngeal phase?

Answer 10

Posterior nares closed which prevents reflux of food
The palatopharyngeal folds are pulled medially allowing food to pass
The epiglottis closes the larynx which inhibits respiration
Upper esophageal sphincter relaxes

The entire process occurring in less than 2 seconds

Question 11

What is the esophageal phase?

Answer 11

Involuntary phase
Exhibits primary and secondary peristalsis

Question 12

What is primary peristalsis?

Answer 12

Continuation of the peristaltic wave that begins in the pharynx

Question 13

What is secondary peristalsis?

Answer 13

Wavesresulting from distention of the esophagus by the retained food
Waves stop when all the food has emptied into the stomach

Question 14

How is peristalsis accomplished?

Answer 14

Circular smooth muscle contract behind
Relaxes in front of the bolus
Longitudinal contraction (shortening) of smooth muscle

Question 15

Describe the function of receptive relaxation of the gastroesophageal/cardiac/lower esophageal sphincter

Answer 15

Allows easy propulsion of swallowed food into the stomach

Question 16

Describe what may cause relaxation and inhibition of the LES

Answer 16

Neuronal vagal inhibitory fibers (VIFs)
Vasoactive intestinal peptide (VIP)
Nitric oxide

Question 17

Describe what may cause contraction and excitation of the LES

Answer 17

Neuronal vagal excitatory fibers (VEFs)
Acetylcholine (ACh)
Substance P

Question 18

What is achalasia?

Answer 18

A condition in which food accumulates in the esophagus and the organ becomes massively dilated

Question 19

What factors may cause achalasia?

Answer 19

Increased resting LES tone
Incomplete relaxation on swallowing due to loss of inhibitory neurons in the myenteric plexus
Defective release of nitric oxide and VIP

Question 20

What are the signs and symptoms of achalasia?

Answer 20

Dysphagia (Solid + liquid)
Regurgitation of food
Weight loss

Question 21

What is gastroesophageal reflux disease (GERD)?

Answer 21

LES remains open causing heartburn and esophagitis and can lead to ulceration and stricture of the esophagus due to scarring

Question 22

What are some potential causes of GERD?

Answer 22

Dysfunctional LES due to CNS depressant medication, pregnancy and hiatal hernia