Chapter 38 – The Digestive and Excretory Systems

1. Chapter 38 – The Digestive and Excretory Systems

2. Four Macromolecules • Proteins • Carbohydrates • Fats/Lipids • Nucleic Acids

3. Proteins – contain amino acids • A simple carbohydrate has one or two monomers (monosaccharide or disaccharide). A complex carbohydrate contains many monomers (polysaccharide). • A lipid is formed from a glycerol backbone and three fatty acids attached.

4. 38-1 Food and Nutrition • We must eat food for energy • Cells convert energy stored in glucose and other molecules into ATP • and raw materials

5. calorie – the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celsius • Calorie– the unit used when nutritionists measure the energy in food • = 1,000 calories = 1 kilocalorie (kcal) • – teenage females need approximately 2,200Calories/day • – teenage males need approximately 2,800Calories/day • – those engaging in vigorous daily exercise require more Calories

6. eating food forraw materials – used to build and repair tissue • used to manufacture new biochemicals(e.g., proteins, phospholipids, DNA) • there are 45 substances the body cannot manufacture (so we must ingest them)

7. nutrition – the study of food and its effect on the body • tries to determine how food helps the body meet all of its various needs • nutritionists– recommend balanced diets with many types of food • plan diets for people with particular needs (e.g., diabetics)

8. Nutrients • the nutrients needed by the body:  water  fats vitamins  carbohydrates proteins minerals

9. Water • needed by every cell for processes and chemical reactions to take place • makes up blood, lymph, and other body fluids • used in sweat to cool the body • lost in urine and water vapor in breath • amount needed • at least 1 liter per day • too little causes dehydration • when too little water is taken in – causes problems in the circulatory and nervoussystems

10. Carbohydrates • main source of energy for the body • complex carbohydrates are broken into simple sugars and absorbed into the bloodstream • glycogen– the form of carbohydrate stored in the liver and muscle • cellulose– fiber; helps move material through the digestive system • ◦ types / where they are found • simple carbohydrates – monosaccharides and disaccharides • fruit, honey, cane sugar • complex carbohydrates – polysaccharides • breads, pastas, cereals, potatoes, vegetables

11. Fat • formed from fatty acids and glycerol • need essential fatty acids to produce cell membranes, myelin sheaths, and certain hormones • help absorb fat-soluble vitamins • protects body organs and insulates

12. Calorie Content • 1 gram of protein = 4 calories • 1 gram of carbs = 4 calories • 1 gram of fat = 9 calories

13. Saturated vs. Unsaturated Fats • saturated fats – fats whose fatty acids contains only single bonds between carbon atoms – has the maximum number of hydrogen atoms – most are solid at room temperature • unsaturated fats – contains at least one double bond in the fatty acid chain – usually liquid at room temperature – polyunsaturated – more than 1 double bond

14. Where are fats found? • sources – oil, butter, lard, nuts, avocado  • amount needed • maximum amount of fat should be 30% of Calories for the day • of which, only 10% should be saturated fat • too much fat can lead to high blood pressure, heart disease, obesity and diabetes

15. Vitamins • function / description • organic molecules that help regulate body processes (often working with enzymes) • 2 types: 1) fat-soluble – can be stored in fatty tissue (vitamin A, D, E, K) 2) water-soluble – cannot be stored in the body (vitamin B, C) • where they are found • most are found in food • bacteria in the intestine make vitamin K; skin produces vitamin D • ◦ too much/too little • too few can be fatal for certain vitamins • too many water-soluble vitamins are of no benefit – they are excreted • too many fat-soluble vitamins can be harmful – they build up in tissues

16. Some vitamins and what they do

17. Proteins Supply raw materials for growth and repair of skin, muscle, etc. • regulatory and transport functions • (e.g., insulin – regulates blood sugar levels • hemoglobin– transports oxygen • polymers of amino acids • essential amino acids – 8 of the 20 amino acids that MUST be eaten • the body cannot manufacture these • all 8 are in meat, fish, eggs, and milk • vegetarians – must eat a combination of plant foods to get all 8 essential amino acids (e.g., beans and rice)

18. Minerals • inorganic molecules that the body needs in small amounts • (e.g., calcium – used for bones and teeth • Found in living tissues of plants and animals • iron– used to make hemoglobin • magnesium– used to synthesize proteins) • body does not metabolize minerals, but they are lost in urine, sweat, and waste

19. Nutrition and Balanced Diet • The Food Guide Pyramid • classifies food into six groups • indicates the number of servings for each group that should be eaten per day • basic idea – eat a variety of foods each day and limit your intake of fatty, sugary food

20. Fats, Oils, and Sweets (use sparingly) Soft drinks, candy, ice cream, mayonnaise, and other foods in this group have relatively few valuable nutrients. Milk, Yogurt, and Cheese Group (2-3 Servings) Milk and other dairy products are rich in proteins, carbohydrates, vitamins, and minerals. Meat, Poultry, Fish, Dry Beans, Eggs, and Nut Group (2-3 servings) These foods are high in protein. They also supply vitamins and minerals. Vegetable Group (3-5 servings) Vegetables are a low-fat source of carbohydrates, fiber, vitamins, and minerals. Fruit Group (2-4 servings) Fruits are good sources of carbohydrates, fiber, vitamins and water. Bread, Cereal, Rice and Pasta Group(6-11 servings) The foods at the base of the pyramid are rich in complex carbohydrates and also provide proteins, fiber, vitamins, and some minerals.

21. Food Labels • provide general information about nutrition • lists: 1) Daily Values • based on a 2,000 Calorie diet • active teenagers often need • more than 2,000 Cal/day • adults often need less than 2,000 Cal/day • 2) Calories per gram of protein, carbohydrate, and fat • use the label to chose a food that is high in nutrition and low in Calories

22. 38-2 The Process of Digestion • alimentary canal – one-way tube that passes through the body • digestive system – helps convert foods into simpler molecules that can be absorbed and used by the cells of the body • includes: mouth pharynx esophagus small intestine  large intestine stomach

23. Accessory Structures • Add secretions to the digestive system salivary glands pancreas liver

24. The digestive system

25. The Mouth • Mechanical Digestion • physical breakdown of large pieces of food into smaller pieces • Chemical Digestion • breakdown of large food molecules into smaller food molecules with digestive enzymes • Mouth • organ in which digestion begins. • contains teeth

26. Teeth • Tear and crush food into a fine paste until it is ready to be swallowed • Anchored to the bones of the jaw; protected by a coating of enamel • Do much of the mechanical digestion

27. Saliva • Secreted by salivary glands as the teeth cut and grind food • Secretion is controlled by the nervous system; can be triggered by scent • Three functions: • 1) helps to ease the passage of food through the digestive system by moistening food  • 2) contains lysozyme – an enzyme that fights infection by digesting the cell walls of bacteria that enter the mouth  • 3) contains amylase – begins to break the bonds in starches to produce simpler sugars salivary glands

28. Esophagus – tube that connects the throat (pharynx) to the stomach – walls are made of ringed muscle that squeeze food through the tube – peristalsis – the rhythmic muscular contractions of the smooth muscle in the digestive system that pushes food along Esophagus

29. Esophagus - continued Bolus – chewed clump of food that is pushed down the throat by the tongue and throat muscles Epiglottis – flap of tissue that covers the trachea when swallowing to prevent food from entering lungs

30. How to keep food from defying gravity… Cardiac sphincter – also called esophageal sphincter – a thick ring of muscle that closes the esophagus after food has passed into the stomach – prevents the contents of the stomach from moving back into the esophagus – heartburn – backflow of stomach acid across the cardiac sphincter – can be caused by overeating, overdrinking, or excess caffeine

31. Stomach Large, muscular sac just below the diaphragm in the abdomen - three layers of smooth muscle - churns and mixes the food that is swallowed Stomach

32. Chemical Digestion in the Stomach chemical digestion – stomach is lined with millions of microscopic gastric glands that release a number of substances into the stomach  gastric secretions include: • 1) mucus – lubricates food and protects the stomach lining • 2) HCl – hydrochloric acid makes the stomach contents acidic which allows pepsin to work • 3) pepsin – enzyme that begins the digestion of protein • works best in acidic environments • breaks proteins into smaller polypeptides • the acidic environment denatures (“changes the shape of”) the amylase enzyme, so carbohydrate digestion stops in the stomach (it restarts in the small intestine)

33. Mechanical Digestion in the Stomach mechanical digestion – muscular walls of the stomach contract to churn and mix stomach fluids and food to produce chyme chyme – a pasty mixture of food that results after 2 to 3 hours of churning in the stomach pyloric valve – a ring of muscle between the stomach and small intestine opens to allow chyme to flow into the small intestine

34. Small Intestine • Three Sections • Duodenum • Jejunim • Ileum • Did you know that if you took out your small intestine and laid it end to end … Small Intestine

35. Duodenum • first of the three parts of the small intestine • where almost all of the digestive enzymes enter the intestines • chyme mixes with enzymes and digestive fluids from the pancreas, liver, and the lining of the duodenum

36. Accessory Structures liver gall bladder pancreas

37. Accessory Structures • pancreas – long organ (gland) located behind the stomach. It serves three functions: • 1) produces hormones that regulate blood sugar levels • 2) produces enzymes that break down carbohydrates, proteins, lipids, and nucleic acids • 3) produces sodium bicarbonate to neutralize HCl from stomach acid – because pancreatic enzymes only work in a neutral environment • liver – large, brownish organ located just above and to the left of the stomach • secretes bile – yellow-brown liquid loaded with lipids and salts • acts like a detergent - breaks fat into smaller and smaller droplets which make it possible for enzymes to reach more surface area • gallbladder – pouch-like organ behind the liver that stores bile

38. Intestinal Secretions • peptidase – breaks down dipeptides into amino acids   • maltase, sucrase, and lactase – breaks down remaining disaccharides into monosaccharides

39. More Parts Liver Bile Duct Gall Bladder Pancreas Pancreatic Duct Duodenum To rest of small intestine…

40. Absorption in the Small Intestine • jejunum and ileum– last two sections of the small intestine • approximately 6 meters long • at this point chemical digestion is complete • nutrient molecules are absorbed from these two sections into the bloodstream • peristalsis moves the chyme along the jejunum and ileum

41. Absorption in the Small Intestine -- continued • villi – finger-like projections that increase the surface area of the walls of the small intestine • microvilli – thousands of even tinier finger-like projections found on the surface of the cells of the villi! • inside each villus is a network of capillaries and lymph vessels • absorption – nutrients are absorbed into the cells of the villi lining the small intestine • carbohydrates and proteins are absorbed into capillaries • undigested fat and some fatty acids are absorbed into lymph vessels

42. The Lining of the Small Intestine Small Intestine Villus Circular Folds Epithelial Cells Villi Capillaries Lymph Vessel Vein Artery

43. Absorption -- Continued • when food leaves the small intestine, it is nutrient-free • only water, cellulose, and other undigestible substances remain • appendix – small sac-like organ in small intestine that does little to promote digestion • Can be clogged and inflamed – appendicitis • Thought to aid in digestion of cellulose in animals.

44. The Large Intestine • large intestine,or colon– removes water from undigested material that is left • bacterial colonies produce compounds like vitamin K • concentrated waste material passes through the rectum and is eliminated

45. Digestive System Disorders • GERD– gastroesophagealreflux disease • chronic heartburn in 25-35% of people • symptoms – heartburn, regurgitation, difficulty swallowing • causes – defects in esophageal sphincter; slower than normal emptying of the stomach; • decreased secretion of bicarbonate by the esophagus • treatments – lifestyle changes; medication to control stomach acid; surgery • peptic ulcer – hole in stomach lining produced by the powerful acids released into the stomach • most are caused by Heliobacter pylori; can be cured with antibiotics • diarrhea – irritation or infection that interferes with the removal of water from the large intestines • constipation – condition resulting from the removal of too much water from the undigested material in the large intestine

46. Recap… salivary glands esophagus liver stomach gall bladder pancreas small intestine large intestine appendix rectum anus

47. §38.3 – The Excretory System • At this point, you are going to put down your notes and just listen for awhile…we’ll fill in the blanks later.

48. What is the excretory system? • The system that eliminates waste in an effort to help the body maintain homeostasis

49. Other Organs in the Excretory System • The skin • Excretes excess water and salts • The Lungs • Excrete carbon dioxide

50. The Heavy Hitters in Excretion • The liver • Takes amino acids (from protein breakdown in other parts of the body) and converts them into other useful products • One of the byproducts is nitrogen waste (ugly stuff) • Liver converts nitrogenous wastes into urea which is removed from the bloodstream by the kidneys.