Unit 5 Notes: Oral Cavity, Esophagus & Stomach Details!

(1) Dig. In The Mouth Both Mechanical & Chemical Digestion Mechanical: Teeth chewing + grinding breaks down food into smaller units Chemical: Enzymes in saliva breaks down parts of food

(2) Saliva & Digestion Saliva = Spit Lubricates food for esophageal transfer Contains an enzyme called AMYLASE… Breaks down starch  maltose

(3) Saliva Reflexes Parasympathetic release of saliva Causes: Pressure in mouth Smell / Sight of food Thinking about food Emotional connection to food

(4) Bolus Bolus = chewed up food, mixed with saliva. Bolus travels from mouth  esophagus.

(5) Deglutition Buccal Phase (Voluntary): (A.K.A. – Swallowing) Buccal Phase (Voluntary): Tongue moves bolus into pharynx Pharyngeal-Esophageal Phase (Involuntary): Epiglottis closes over larynx Bolus moves into esophagus

(6) In The Esophagus Bolus moves from esophagus  stomach Food moves through esophagus using PERISTALSIS: Peristalsis = Involuntary contraction of muscle Wave-like contractions push food down Like a tube of toothpaste!

(7) 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

(8) 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.

(9) 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

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

(11) 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.

(12) 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