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9 Cards in this Set
- Front
- Back
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Stomach Anatomy: Functional Regions
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1) Proximal (Fundus) 2) Distal (Antrum)
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Stomach Proximal Region Function
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Responsible for receiving ingested meal
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Stomach Distal Region Function
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Responsible for contractions that mix food and propel it into
duodenum |
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Motility Function
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1) Storage 2) Mixing 3) Emptying
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Motility Function: Storage
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a. proximal stomach relaxes to accommodate ingested meal by process called
receptive relaxation b. pressure returns slowly to basal levels c. receptive relaxation mediated by vagovagal reflex, which is initiated by distension of stomach and is abolished by vagotomy d. stomach can hold up to 1.5 liters with little change in pressure |
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Motility Function: Mixing
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1) Presence of food causes distal stomach to increase contractions 2) Contractions: A) Mix food with gastric secretions B) Reduces size of particles 3) Food mixed into pasty consistency called chyme
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Motility Function: Emptying
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Distal stomach contracts to propel food into duodenum
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Peristalsis
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1) Contractions originate in pacemaker region in midstomach and proceed distally 2) As they move distally toward pylorus increase in: A) Velocity B) Force 3) Wave of contraction closes: A) Distal antrum B) Pyloric sphincter before chyme
reaches there 4) Causes most of chyme to be propelled back into stomach to be mixed (retropulsion) 5) During fasting, contractions called migrating myoelectric complexes occur at 90 minute intervals (motilin) A) Clear the stomach of any residual food B) Cause hunger contractions if stomach has been empty for about 2 hours C) Abolished by eating 6) Hunger pangs start 12-24 hours after last meal and continue for 3-4 days before subsiding |
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Gastric Emptying
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1) Occurs when chyme decomposed into small enough pieces to fit through pyloric sphincter (may take ~3 h) 2) Rate depends on type of food ingested 3) Liquids empty faster than solids 4) Carbohydrate-rich food leaves faster than protein-rich food, which leaves faster than fat-rich food 5) Rate inversely proportional to pressure in proximal stomach, which increases slowly during digestive period 6) Controlled mostly by signals from duodenum 7) Inhibited by: A) High [H+] B) Fat C) Protein D) Non-isotonic solutions E) Increased distension of proximal stomach F) Increased pressure in proximal small intestine 8) Prevents flow of chyme from exceeding ability of intestine to handle it
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