Notes: The Stomach Tuesday

(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 protein Rennin = Enzyme = Breaks down protein Muccin = 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