1. Digestive System

2. Mouth Esophogus Liver Anus Stomach Pancreas Large intestine Small intestine Rectum

3. Digestion: Accessory Organs Liver Gall Bladder Pancreas

4. Why Do We Eat? Regardless of what an animal eats, an adequate diet must satisfy three nutritional needs –Fuel for all cellular work –The organic raw materials for biosynthesis –Essential nutrients, substances such as vitamins that the animal cannot make for itself

5. Nearly all of an animal’s ATP generation –I–Is based on the oxidation of energy-rich molecules: carbohydrates, proteins, and fats

6. Glucose is a major fuel for cells Its metabolism, regulated by hormone action, is an important example of homeostasis 1 When blood glucose level rises, a gland called the pancreas secretes insulin, a hormone, into the blood. Insulin enhances the transport of glucose into body cells and stimulates the liver and muscle cells to store glucose as glycogen. As a result, blood glucose level drops. 2 STIMULUS: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood STIMULUS: Blood glucose level drops below set point. Glucagon promotes the breakdown of glycogen in the liver and the release of glucose into the blood, increasing blood glucose level. 4 When blood glucose level drops, the pancreas secretes the hormone glucagon, which opposes the effect of insulin. 3

7. When fewer calories are taken in than are expended –F–Fuel is taken out of storage and oxidized

8. Obesity as a Human Health Problem The World Health Organization –N–Now recognizes obesity as a major global health problem Obesity contributes to a number of health problems, including –D–Diabetes, cardiovascular disease, and colon and breast cancer

9. Caloric Imbalance Undernourishment –Occurs in animals when their diets are chronically deficient in calories –Can have detrimental effects on an animal

10. Overnourishment –R–Results from excessive food intake –L–Leads to the storage of excess calories as fat 100 µm The White House's task force on childhood obesity is tackling obesogens and the Environmental Protection Agency has pumped $20 million into studying them. BONUS!!!! http://www.motherearthnews.com/natural- health/atrazine-probable-obesogen- zwfz1202zhun.aspx#axzz2NX2P5Mmb

11. Researchers have discovered –S–Several of the mechanisms that help regulate body weight Over the long term, homeostatic mechanisms –A–Are feedback circuits that control the body’s storage and metabolism of fat

12. Several chemical signals called hormones –R–Regulate both long-term and short-term appetite by affecting a “satiety center” in the brain Produced by adipose (fat) tissue, leptin suppresses appetite as its level increases. When body fat decreases, leptin levels fall, and appetite increases. Leptin PYY Insulin Ghrelin Secreted by the stomach wall, ghrelin is one of the signals that triggers feelings of hunger as mealtimes approach. In dieters who lose weight, ghrelin levels increase, which may be one reason it’s so hard to stay on a diet. The hormone PYY, secreted by the small intestine after meals, acts as an appetite suppressant that counters the appetite stimulant ghrelin. A rise in blood sugar level after a meal stimulates the pancreas to secrete insulin (see Figure 41.3). In addition to its other functions, insulin suppresses appetite by acting on the brain. http://www.youtube.com/watch?v=BwqAel WSgHk

13. The complexity of weight control in humans –I–Is evident from studies of the hormone leptin Mice that inherit a defect in the gene for leptin –B–Become very obese

14. Obesity and Evolution The problem of maintaining weight partly stems from our evolutionary past –W–When fat hoarding was a means of survival –*–*Journal Entry – Article Summary! – TYPED – DUE MONEY!

15. A species of birds called petrels –B–Become obese as chicks due to the need to consume more calories than they burn Figure 41.7

16. Digestion The process of PHYSICALLY (mechanically) and CHEMICALLY… Changing the composition of food into simpler substances that your cells can use for growth, repair and maintenance.

17. Digestive System As food is digested, it passes through a muscular tube leading from the mouth to the (GASTROINTESTINAL TRACT/ GI TRACT).As food is digested, it passes through a muscular tube leading from the mouth to the (GASTROINTESTINAL TRACT/ GI TRACT). The GI tract is about 25 to 30 feet in length and each part plays very important functions!The GI tract is about 25 to 30 feet in length and each part plays very important functions!

18. Digestion: Physical/Mechanical Changes Grinding and mixing by teeth (MASTICATION) in the mouth and muscular actions of the stomach and small intestine and…Grinding and mixing by teeth (MASTICATION) in the mouth and muscular actions of the stomach and small intestine and… Liquefying by the addition of water and digestive juices in the mouth, stomach and small intestineLiquefying by the addition of water and digestive juices in the mouth, stomach and small intestine

19. Digestion: Chemical Changes In Chemical Digestion, food is mixed with powerful acids and enzymes!In Chemical Digestion, food is mixed with powerful acids and enzymes! Complex nutrients are broken down into particles usable by cells:Complex nutrients are broken down into particles usable by cells: -Polysaccharides and disaccharides to monosaccharides (carb chains) -Proteins to amino acids -Fats to fatty acids to glycerol

20. Chemical Environment of the GI Tract Neutral in mouth -(pH approx 7) Acid in stomach -(pH approx 2) Neutral in small intestine - (pH approx 7)

21. Enzymes Big food molecules can’t pass through cell membranes.Big food molecules can’t pass through cell membranes. ENZYMES are types of proteins used to break up big molecules into small ones (they act like chemical scissors).ENZYMES are types of proteins used to break up big molecules into small ones (they act like chemical scissors). These small molecules can pass through the wall of the small intestine into the blood. They then pass into cells and are used.These small molecules can pass through the wall of the small intestine into the blood. They then pass into cells and are used.

22. Big food molecules can’t pass through cell walls. ENZYMES are used to break up big molecules into small ones (they act like scissors). These small molecules can pass through the wall of the small intestine into the blood.

23. Digestion: Mouth Physical Changes: - First step in digestion - Teeth grind food -Salivary glands add water (99%) Chemical Changes: -Salivary amylase (digests starch…big sugars) aka. polysaccharides

24. Digestion: Esophagus Transport tube (10 inches) Muscular (muscular contractions move the food - peristalsis) Enables swallowing to move bolus (food) from the mouth to the stomach No enzymes added Other tube in the throat region?

25. Digestion: Stomach (3 hrs) pH Shift Gastric Glands in Stomach produce gastric juices containing 3 types of cells 1.Mucus – lubricates/protects 2.Chief – pepsinogen (inactive pepsin) + HCL - pepsin 3.Parietal – secretes HCL (pH 2..STRONG) pH rapidly decreases Protein digestion begins in the stomach as the major gastric enzyme that begins to break down protein is PEPSIN. The mixture of food and gastric juices is called chyme…and it moves to the SI next!!

26. Gastric Ulcers Lesions in the lining Mainly caused by bacterium Helicobacter pylori 1 µm Bacteria Mucus layer of stomach

27. Digestion: Small Intestine(SI) – 5-14 hours About 95% of digestion takes place in SI Coiled and folded Made of 3 sections: duodenum (12 inches), jejunum (4ft) and ilium (5ft)….can stretch to over 20 feet!! Peristalsis moves food through the SI Another pH shift…what happens? Bile from the liver and digestive enzymes from the pancreas (proteases ex: trypsin for protein digestion, pancreatic amylase for carbohydrate digestion and pancreatic lipase for fat digestion) further break down food

28. Liver Bile Acid chyme Stomach Pancreatic juice Pancreas Intestinal juice Duodenum of small intestine Gall- bladder

29. Small Intestine – Site of Nutrient Absorbtion!!! Walls of intestine pleated with folds covered with villi. (increase surface area) Function is to absorb nutrients in to the BLOODSTREAM

30. Digestion: Large Intestine (aka: colon) – up to 3 days The small intestine is connected to the large intestine (3-5 feet long in the body…5-6 stretched) Chyme is very liquid when enters the LI, so main function is to ABSORB WATER!! Solid wastes called feces leave through the rectum and then finally out the anus (mucus/bile/cells from lining of LI and water)

31. Accessory Organs Pancreas – gland behind stomach – secretes bicarbonate to neutralize environment of SI, produces 3 digestive enzymes to break down carbs, protein and fat. Carbs – Pancreatic Amylase Protein – Fat – Liver – large gland above stomach. Produces digestive juice called bile. (Helps to digest fat) Gall Bladder – muscular sac that stores bile

32. Match the organ to its function!! Mouth 1. This is where water is absorbed. Esophogus 2. Makes bile which breaks up fats and it is alkaline to give the right pH for the enzymes in the S. intestine. Stomach 3. Makes all 3 enzymes. Liver 4. Mixes the food with enzymes that digest proteins AND contains acid to kill bacteria. Pancreas 5. Produces more enzymes AND this is where the food is absorbed through the gut wall into the blood. Small intestine 6. Chew and mix the food with saliva (contains enzymes). Large intestine 7. Links the mouth to the stomach. Rectum 8. Here food that can’t be digested is stored as faeces and then leaves through the anus.

33. Well Done!!