CHAPTER 22: THE DIGESTIVE SYSTEM. Jayda Cortez Kimberly Navarro

Transcription

1 CHAPTER 22: THE DIGESTIVE SYSTEM Jayda Cortez Kimberly Navarro

2 Objectives - Describe the functions of the organs that make up the digestive system - Identify and describe the four stages of food processing - Name and describe disorders and diseases of the digestive system.

3 Importance of the Digestive System/Function - Function: ensure proper digestion and absorption of nutrients Food are made up of complex molecules. -Digestive system take those complex molecules to break down into simple molecules for them to pass through the cell membranes.

4 The Four Stages of Food Processing - Ingestion: eating - Digestion: The breakdown of food to nutrients for the body to absorb. - Absorption: Nutrients go into the bloodstream - Elimination: Disposal of undigested material

5 The Mouth - Ingestion and preliminary steps of digestion take place here. - Mechanical digestion: Grinding of food. - Chemical digestion: Salivary glands excrete saliva to break down the bonds through enzymatic hydrolysis. - Tongue shapes food into a ball and pushes it to the back of the mouth.

6 Salivary Glands -Saliva: 1. Serous type: watery and contains enzymes (salivary amylase) 2. Mucous type: thick, slippery, and contains mucous; no enzymes; lubricates food during mastication -3 pairs of salivary glands: 1. Parotids: largest; produces serous type of saliva 2. Submandibular: produces both serous and mucous type of saliva; ducts open on either side of lingual frenulum 3. Sublingual: produce only mucous-type saliva; opens via 10 to 15 ducts into the floor of the mouth.

7 The Pharynx (throat) - Connects the mouth to esophagus. - Opens to the trachea. - Epiglottis ensures the food goes down the esophagus.

8 The Esophagus - Muscular tube that connects the pharynx to the stomach; about 25 centimeters (10 inches) long - Passageway for food--- moves food by peristalsis - Peristalsis: alternating waves of muscular contraction and relaxation that squeeze the food ball along the esophagus.

9 The Stomach - The stomach holds enough food to sustain us for a couple of hours. - Gastric juice is made of strong acid, digestive enzymes, and mucus. - Gastric juice mixes with food and produces chyme. - Mucus protects the stomach from digesting itself.

10 The Small Intestine - Approximately 7 meters long (20 feet); 2 cm or so in diameter - Divisions: 1. Duodenum 2. Jejunum 3. Ileum - Where greatest amount of digestion and absorption occurs - Wall--- contracts to produce peristalsis and segmentation movement - Digested nutrients are absorbed through intestinal walls - Has a lining covered with fingerlike projections called villi which are covered with smaller hairlike structures called microvilli. increases the surface area of villus for absorption of nutrients

11 Liver and Gallbladder - The liver produces bile, which is stored in the gallbladder. - Bile contains salts that keep fat into droplets to be digested faster.

12 Pancreas - Exocrine gland that lies behind the stomach - Pancreatic islets (of Langerhans) : secrete hormones glucagon and insulin into the blood - Produces juice that contains enzymes (such as amylase, protease, lipase) To break down carbohydrates, protein and fats. - Secretes pancreatic juice into pancreatic ducts

13 The Large Intestine - The main part is the colon, which is twice as wide as the small intestine. - Absorbs water from the alimentary canal. - Undigested materials solidify as water is absorbed. - Approximately 1.5 meters long.

14 Appendix - Hangs on the right side of the large intestine - Has no important digestive functions in humans Anus - The opening in the end of the alimentary canal; where feces is excreted - Regulate by 2 rectal sphincters ( 1 voluntary and 1 involuntary) when the voluntary sphincter is relaxed, contractions of the rectum expel feces

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16 Nutrition and Metabolism - Cellular respiration breaks down molecules and extracts the energy. - Metabolic rate is the rate of energy consumption by the body amino acids make all proteins. 12 can be manufactured by the adult body. - Vitamins are organic molecules required in our diets. - Minerals are smaller chemical elements that are in the form of inorganic nutrients. - Essential fatty acids are fatty acids we cannot make, so we obtain them through our diet

17 Obesity - Too high body mass index (BMI: ratio of weight and height) - Cause: Eating more calories than you burn in (on a long-term basis) -poor diet, genetics, and lack of sleep, etc - an epidemic in the United States (about ⅓ of Americans are obese; ⅓ overweight) - Increases the risk of heart attack, diabetes and other several diseases.

18 Fun Facts - Average person produces 2 pints of saliva every day = 2 cans of soda - Food doesn t need gravity to get to your stomach. Because of peristalsis, food will be push down to the stomach even when you are upside down. - Small intestine is approximately 2,700 in. = Over half the size of the basketball court.

19 Citations Thibodeau, Gary A., Kevin T. Patton, and Catherine Parker Anthony. Structure & Function of the Body. 14th ed. St. Louis, MO: Elsevier/Mosby, Print. Moores, Danielle. "Obesity: Causes, Complications, and Diagnosis." Healthline. Healthline Media, 16 July Web. 21 Aug