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GI Motility - Esophagus Inc Tone with ingestion of meal o...

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Esophagus Motility Functions - Transfer food from mouth stomach Deglutition - Can be initiated voluntarily but typically is “triggered” (swallow is triggered to some extent) o Swallowing center uses input from mechanoRs in pharynx to recognize when food bolus is suitable for swallowing - Complex reflex to insure the bolus esophagus - Terminal part of reflex initiates o Primary peristalsis in esophagus o Relaxation of LES o Receptive relaxation in stomach - The UES in Deglutition o Formed primarily by the circopharyngeus muscle o Remains closed unless it needs to be open (e.g., during deglutition, belching, vomiting) Helps to prevent aspiration of refluxed esophageal contents Helps to prevent diversion of air into esophagus during respiration Contraction of USE increases during inspiration - There’s 4 places that the bolus can fall into 1. Mouth 2. Nosapharynx 3. Trachea 4. Esophagus (most ideal) - Process of Deglutition - Soft palate moves upward, closing off the nasopharynx - Epiglottis swings downward and largynx moves upward, closing off the trachea - Upper Esophageal Sphincter (UES) relaxes, allowing bolus to enter the esophagus - Muscles in posterior wall of pharynx are activated sequentially wave of transverse contractions, pushing bolus through the UES - Involves up to 25 SKM (swallowing center sends motor response to muscles via somatic motor neurons travelling in various CNs and cervical spinal nerves Motility Patterns - Primary peristalsis o Initated by swallowing center as part of swallowing reflex o Sequential activation of contractions along the entire length of the esophagus - Secondary peristalsis o Initiated by residual food bolus (peanut butter sandwich) o Starts just above food bolus o Vago-vagal reflex (long reflex) Striated muscle portion, smooth muscle portion o Local reflex in ENS (short reflex) Smooth muscle portion only Regulations of the LES - Tonic contractions o Myogenic mechanism o Can be modulated by neural/hormonal input/stretch - Inc. Tone with ingestion of meal o Prevents reflex (LES pressure > intra-abdominal pressure o Protects squamous epithelium lining the esophagus o Mediated by Ach and gastrin (increase tone) o Depends on composition of meal (protein> fat) - Swallow-induced relaxation o Initiated by swallowing center as part of swallowing reflex o Relaxation precedes arrival of peristaltic wave o Mediated by NO/VIP from inhibitory enteric neurons o Innervated by parasympathetic preganglionic fibers in CN- X
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Stomach Motility Function - Mixing/grinding ingested food emulsion of small particles (chyme) o Inc. surface area accessible to digestive enzymes - Regulating delivery of chyme to small intestine o Match delivery to digestive/absorption capacities of small intestine Motility Patterns - Proximal stomach (cardia, fundus, proximal body) o Tonic contractions ( “driving pressure” for gastric emptying) - Distal stomach (distal body, antrum) o
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