Lecture 38 11/15/23 Flashcards
What movements fall into GI tract motility?
-propulsive
-retentive
-mixing
What is transit time?
time it takes for ingesta to travel from one portion of GI tract to another
What are the functions of GI movements?
-propel ingesta from one location to the next
-retain ingesta at a given site for digestion, absorption, or storage
-break up food material and mix it with digestive secretions
-circulate ingesta so it comes in contact with digestive/absorptive surfaces
What are the characteristics of slow waves?
-slow, rhythmic movements
-slow changes in resting membrane potential
-NOT action potentials/do not cause contraction
-frequency varies by location
-determine maximum rate of muscle contractions
What are the characteristics of the interstitial cells of Cajal?
-pacemaker cells
-generate slow waves
-form network between smooth muscle layers
-connected by tight junctions
What happens when excitatory peptides, like acetylcholine, are released into an area of GI tract?
increase in cell membrane potential and contraction
What happens when inhibitory peptides, like norepinephrine, are released into an area of GI tract?
decreased cell membrane potential and no contraction
What is the overarching function of propulsive movements?
move food forward through the GI tract
What are the characteristics of contraction during peristalsis?
-contractile ring behind bolus
-relaxation of muscle in front of bolus
What are the potential stimuli for peristalsis?
-distension of gut
-physical or chemical irritation of gut lining
-strong parasympathetic NS signals
What are the functions of mixing movements?
-grinding/mixing food material with digestive enzymes
-allowing food to come in contact with gut mucosa for absorption
What are the characteristics of prehension?
-process of getting food into the mouth
-involves coordination of small, voluntary muscles of the face/lips/tongue
What are the characteristics of chewing/mastication?
-first act of digestion
-breaks food down small enough to pass through esophagus
-moisten and lubricate food by mixing with saliva
What are the four phases of swallowing/deglutition?
-oral preparatory phase
-oral propulsive phase
-pharyngeal phase
-esophoageal phase
What are the characteristics of the oral preparatory phase of swallowing?
-voluntary
-food enters oral cavity
-chewing
-bolus formation
What are the characteristics of the oral propulsive phase of swallowing?
-voluntary
-tongue elevates and propels bolus to pharynx
What are the characteristics of the pharyngeal phase of swallowing?
-involuntary
-bolus in caudal pharynx stimulates mechanoreceptors
-soft palate elevates to seal nasopharynx
-epiglottis covers trachea and stops respiration
-pharyngeal wave occurs as upper esophageal sphincter relaxes/opens
What are the characteristics of the esophageal phase of swallowing?
-involuntary
-bolus passes into esophagus
-esophagus contracts sequentially
-lower esophageal sphincter relaxes
-bolus enters stomach
What are the three segments of the esophagus?
-upper esophageal sphincter
-body
-lower esophageal sphincter
What is primary peristalsis of the esophagus?
-peristaltic wave from pharynx to stomach
-initiated by swallowing