VTPP 423 Lecture Notes - Lecture 17: Achalasia, Gastroparesis, Area Postrema
6 Nov 2019
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4 major activities of the gastrointestinal tract: motility, secretion, digestion, absorption
Motility
● Propel ingested food from mouth to rectum and mixes and reduces the size of food
● Rate at which food is propelled is regulated to optimize the time for digestion
● Chewing
○ Functions:
■ Mix food with saliva, lubricating it to facilitate swallowing
■ Reduce the size of food particles which facilitates swallowing
■ Mix ingested carbohydrates with salivary amylase to begin carb digestion
○ Involuntary - reflexes initiated by food in mouth
○ Voluntary - override involuntary at any time
● Swallowing - three stages
○ Oral stage: initiates swallowing; mastication and formation of bolus
■ Voluntary
○ Pharyngeal stage: passage of food through the pharynx into esophagus
■ Involuntary
○ Esophageal stage: promotes food from pharynx to stomach
■ Involuntary
■ Motility disorders of esophagus
● Oropharyngeal dysphagia: difficulty swallowing; high prevalence in
neurological diseases
● Achalasia: esophageal motor disorder
○ Insufficient relaxation of LES
● GERD: damage to esophagus due to acid reflux from stomach
● Stomach
○ Accommodation of a meal
■ Orad region
○ Mixing of food with gastric juices
■ Caudad region
○ Movement of material into duodenum
■ Gastric emptying
● Phase of propulsion: rapid flow of liquid, slow movement of large
particles
● Phase of emptying: emptying of liquids; large particles retained in
antrum
● Phase of retropulsion: large particles; clearing of terminal antrum
○ Problems in gastric motility
■ Vomiting: expulsion of gastric contents
● NOT reverse peristalsis; stomach + esophagus are relaxed
● Coordinated by vomiting center in medulla
■ Gastroparesis: impaired gastric emptying
