1. Unit 5 Notes: The Stomach

2. (1) About The Stomach
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

5. (2) Dig. In The Stomach Mechanical Digestion: Chemical Digestion:
Peristaltic churning of stomach muscle breaks apart bolus.
Triggered by release of serotonin from rugae
Chemical Digestion:
Gastric Juice contains enzymes and acid that breaks down bolus.

7. (3) 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

9. (4) Gastric Juice Contains… HCl = Hydrochloric Acid
Pepsin = Enzyme = Breaks down protein
Rennin = Enzyme = Breaks down protein
Muccin = Mucus = Lubricate Food Mass

10. (5) 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.

11. (6) Leaving 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