Digestive System

Digestive system’s role is to break down ingested food into molecules that are small enough to be absorbed by the body. Eliminate solid waste

Anatomy of the Digestive System Remember: Organs of the digestive tract are Divided into two groups Part I: Digestive Tract (6 parts) 1. Mouth 2. Pharynx 3. Esophagus 4. Stomach 5. Small Intestine 6. Large Intestine Digestive tract: mouth to anus, tube 4 to 6 m in length surrounded by muscles –crush food and move it along

Part II: Digestive Glands (secrete substances) 1. Salivary Glands 2. Liver 3. Pancreas 4. Gastric Glands 5. Intestinal Glands Digestive Glands: secrete substances that aid in the digestion of food (found either in the digestive tract or attached to it).

Processing Food Ingestion and propulsion of food Digestion of food Absorption of nutrients Elimination of fecal matter

Ingestion: act of taking substances into the body through the mouth. Ex. Food etc. Two mechanisms: Deglutition: swallowing the food Peristalsis: muscular contractions of the esophagus, stomach, small intestine, and large intestine which move substances through the digestive tract.

Deglutition (Swallowing): 1. Epiglottis closes the trachea 2. Uvula closes the nasal cavity 3. Food travels without getting into the respiratory tract

Digestion The transformation of food into nutrients that can be used by the body. Two types: 1. Mechanical transformation consists of physically breaking down food into smaller substances in preparation for chemical transformation a) Chewing: crushing & grinding (teeth, muscles of mouth) b) Churning: muscle contractions mix food with digestive secretions (stomach, SI)

2. Chemical transformation: breaks down the complex molecules of food into simpler molecules. These changes occur with the help of secretions from the digestive glands. Remember: Nutrients are foods that can be absorbed by the body Copy Table 6.15 p. 170 into your notes!

Digestion of Proteins, Carbohydrates, and Fats

2. Carbohydrates

3. Fats

Absorption of Nutrients Passage of nutrients from the digestive tract into the blood or lymph Most food absorbed in small intestine Folds called villi increase surface area for absorption (in lining contains blood and lymph vessels)

Elimination of Fecal Matter Large Intestine: 1. Residue - contains little nutrient matter - arrives in liquid form 2. Water in residue gradually absorbed. 3. By rectum, very little water left (feces solid) 4. Feces expelled through anus

l Copy 6.18 p. 172 see worksheet