Swallowing Flashcards
What is the structure of the alimentary canal?
Mucosa
Submucosa
Muscularis
Serosa
What are the components of the mucosa?
Epithelium
Lamina propria (areolar connective tissue + lymphatic tissue)
Muscularis mucosae (smooth muscle)
What are the components of the submucosa?
Areolar connective tissue
Blood and lymphatic vessels
Neurons - submucosal plexus (Meissner plexus)
What are the components of the muscularis?
Smooth muscle (Circular and longitudinal): Enables peristalsis and segmental contraction
Neurons – myenteric plexus (Auerbach plexus)
What are the components of the serosa?
Connective tissue & epithelium
What are the muscles of chewing innervated by?
Mandibular branch ofcranial nerve V
What are the stages of swallowing?
Stage 1: Oral (buccal) phase
Stage 2: Pharyngeal phase
Stage 3: Esophageal phase
What is the oral phase?
Voluntary stage
Food is squeezed or rolled posteriorly into the pharynx by the tongue
Once initiated, it cannot be stopped
What is the pharyngeal phase?
Involuntary phase
Food entering the pharynx stimulates epithelial swallowing receptor areas, passing impulses to the brain stem which initiates automatic pharyngeal muscle contractions
What are the stages of the pharyngeal phase?
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
What is the esophageal phase?
Involuntary phase
Exhibits primary and secondary peristalsis
What is primary peristalsis?
Continuation of the peristaltic wave that begins in the pharynx
What is secondary peristalsis?
Wavesresulting from distention of the esophagus by the retained food
Waves stop when all the food has emptied into the stomach
How is peristalsis accomplished?
Circular smooth muscle contract behind
Relaxes in front of the bolus
Longitudinal contraction (shortening) of smooth muscle
Describe the function of receptive relaxation of the gastroesophageal/cardiac/lower esophageal sphincter
Allows easy propulsion of swallowed food into the stomach
Describe what may cause relaxation and inhibition of the LES
Neuronal vagal inhibitory fibers (VIFs)
Vasoactive intestinal peptide (VIP)
Nitric oxide
Describe what may cause contraction and excitation of the LES
Neuronal vagal excitatory fibers (VEFs)
Acetylcholine (ACh)
Substance P
What is achalasia?
A condition in which food accumulates in the esophagus and the organ becomes massively dilated
What factors may cause achalasia?
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
What are the signs and symptoms of achalasia?
Dysphagia (Solid + liquid)
Regurgitation of food
Weight loss
What is gastroesophageal reflux disease (GERD)?
LES remains open causing heartburn and esophagitis and can lead to ulceration and stricture of the esophagus due to scarring
What are some potential causes of GERD?
Dysfunctional LES due to CNS depressant medication, pregnancy and hiatal hernia
