THE DIGESTIVE SYSTEM A.K.A. THE GASTROINTESTINAL (GI) TRACT Converts foods into simpler molecules, then absorbs them into the blood stream for use by cells

Mechanical verses Chemical Digestion 1. Mechanical digestion: breaks food into smaller pieces a. increases the surface area of food 2. Chemical digestion: changes the chemical composition of the food a. breaks food down into smaller polymers and individual monomers b. Uses digestive enzymes to break down food

MOUTH & Salivary Glands 1. Teeth – cut & grind food a. This is mechanical digestion 2. Salivary Glands – moisten mouth & food with saliva, which has amylase to break down starches a. This is chemical digestion b. Carbohydrates are the only foods that undergo partial chemical digestion in the mouth

ESOPHAGUS 1. Esophagus –food tube leading to stomach 2. Peristalsis – smooth muscle involuntary contractions to push food into stomach (also moves food through small intestines)

STOMACH 1. Large muscular sac which: a. secretes mucus (to protect stomach) b. secretes hydrochloric acid which activates pepsin (digests protein -- chemical digestion) c. churns food & liquid into “chyme” (mechanical digestion – because the process coats the food with digestive enzymes)

SMALL INTESTINE 1. Where most of the chemical digestion & nutrient absorption occurs 2. Villi – tiny projections that increase surface area for absorption 3. Microvilli – tiny projections on the surface of villi – creates even more surface area for digestion and nutrient absorption

LARGE INTESTINE 1. Also called the colon 2. Water is removed from the materials leaving the small intestine to form solid waste 3. Bacteria in large intestines produce vitamins B & K 4. Diarrhea: large intestines do not absorb enough water 5. Constipation: large intestines absorb too much water PERISTALSIS

RECTUM 1. Holds solid wastes, called feces, until they exit the body through the anus

A. SALIVARY GLANDS B. MOUTH C. ESOPHAGUS D. STOMACH E. LARGE INTESTINE F. SMALL INTESTINE H. ANUS G. RECTUM

PANCREAS 1.Produces digestive enzymes that break down carbohydrates, proteins, and fats 2. The enzymes are released into the small intestine 3. Produces insulin

LIVER & Gall Bladder 1. Liver: Largest internal organ a. Secretes bile which helps aids in fat digestion; breaks fat into smaller fat particles – mechanical digestion b. Stores excess glucose 2. Gall Bladder: stores bile until needed by the small intestines to digest lipids

LIVER PANCREAS GALL BLADDER