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(1) Overall Function
Break down “bolus” from esophagus.Metabolize ALL Carbohydrates.Begin Protein Metabolism.Turn “bolus” into liquid Small Intestine
(2) The Stomach as a Chamber
Stomach can contain up to 1.5L of food without pressure changes.
– Feelings of discomfort come from irritants + too much food
Stomach composed of excess tissue Folds of Tissue = Rugae
– Folds allow the stomach to expand– Folds also contain secretion glands
Food sits in the stomach for 3-4 hours– Depends on Amount & Type of food
(3) Contraction & Churning
Stomach composed of smooth muscle:– Contains 3 layers of muscle = STRONG– Contracts via peristalsis
Peristalsis used to Toss & Churn (not squeeze through).– Like Shake & Bake
Contractions stimulated by release of Serotonin from Rugae.
(4) Release of Gastric Juice
Gastrin (hormone) released from G-Cells within Rugae:– Triggered by smell + taste of food– Triggered by increase in pH
Gastrin stimulates release of HCl = Decreasing pH:– Proteins & Carbohydrates Metabolized– Small & Large Intestine stimulated
(5) Gastric Juice
HCl = Hydrochloric Acid Pepsin = Enzyme = Breaks down proteinRennin = Enzyme = Breaks down proteinMuccin = Mucus = Lubricate Food Mass
(6) Protein Metabolism
Proteins take a lot of Gastric Juice to Metabolize.
Breaking Down Proteins releases H+ ions.
Decreases pH of stomach.G-Cells stop releasing gastrin HCl
stopped.
(7) Exiting the Stomach
The mass leaving the stomach is called “Chyme”:– Mostly liquid Liquids leave first!– Solids are left behind until broken down
Approximately 3mL of food leaves at one time….– Food Exits the Pyloric Sphincter– Chyme dumped into Small Intestine
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