Chapter 21: Digestive and Excretory Systems

1. Chapter 21:Digestive and Excretory Systems

2. 21.1 Nutrition • Nutrition: The process of getting the food needed to survive. • Food provides energy and raw materials. • Malnutrition: Occurs when a person does not get enough to eat, or when the food eaten does not provide all of the nutrients needed.

3. Nutrients: • The raw materials that the body gets from food. • Carbohydrates • Proteins • Fats • Vitamins • Minerals • Water • All are needed by the body each day complete metabolic jobs.

4. Carbohydrates: • The main energy source for the body. • Sugars and starches are broken down for energy. • Sugars: Simple carbohydrates. Make food sweet. • Sugar, honey. • Starch: Complex carbohydrate. • Bread, pasta, potatoes.

5. Fiber: Complex carbohydrate from the cell walls of plant cells. • Not broken down by body, but keeps the digestive system running smoothly. • Peas, beans, fruits, vegetables, whole grains.

6. Protein: • Building blocks of muscle, hair, skin, nails… • Includes 20 amino acids. • Essential amino acids: The nine amino acids that the body cannot make, so needed in the diet. • Complete proteins: Contain all 20 amino acids. • Animal products.

7. Fats (lipids): • Are part of the cell membrane, nerve insulation, and hormones, are an energy source, and store energy. • Saturated fats: Solid at room temperature. • Usually from animal products. • Unsaturated fats: Liquid at room temperature. Oils. • Usually from plant products.

8. Vitamins: • Complex organic molecules that help the body build tissues and molecules, help regulate body functions, and fight disease. • Water soluble vitamins: Cannot be stored by the body. • Vitamin C and the B vitamins. • Fat soluble vitamins: Can be stored in fat tissue. • Vitamins D, E, A, and K.

9. Minerals: • Inorganic molecules that are needed for metabolic functions. • Make bones hard, enable nerve impulses and muscle contraction, keep fluid balance, and are incorporated into proteins. • Examples: calcium, sodium, potassium, iron.

10. Water: • Part of most chemical reactions in the body. Constantly recycled in cells, but needs replaced because some is lost through urination, sweating, and breathing. • Found inside and around cells. • Largest component of blood. • Dehydration: Occurs when water is not replaced in the body.

11. Calorie: • How energy stored in food is measured. • 1 Calorie in heat raises 1 kilogram of water 1 degree Celsius. • If a person consumes more Calories than are burned through metabolism, then the excess energy is stored as fat.

12. Balanced diet: • Meals that contain all of the nutrients that the body needs.

13. Previous Food Pyramid

16. www.mypyramid.gov

17. 21.2 The Process of Digestion • Digestive tract: Tube with the mouth at one end and the anus at the other end. • Ingestion: The process through which food enters the digestive tract.

18. Digestion: • The process of breaking down food into small particles that can pass through cell membranes. • Mechanical digestion: Food is physically chopped up. Creates more surface area for chemical digestion. • Chemical digestion: Chemicals break the bonds in large molecules.

19. Enzymes: • Proteins that speed up chemical reactions. • An enzyme is not changed in the reaction.

20. Digestive organs:

21. Mouth: • Teeth: Chop food into smaller pieces (mechanical digestion). • Salivary glands: Release saliva, which contains enzymes to start chemical digestion (breaks down starches) and water to soften food. • Tongue: Pushes food around mouth and mixes it with saliva.

23. Taste buds: On top of tongue. • Sense sweet, sour, salty, savory (umami), and bitter.

24. Bolus: • Small food mass that has been chewed and mixed with saliva. • Epiglottis: Flap of cartilage that covers opening of trachea to prevent food from entering the respiratory tract.

25. Esophagus: • Tube that connects the pharynx to the stomach. • Lined with cells that secrete mucus to keep the bolus wet. • Smooth muscles tissue along the tube contracts in waves (peristalsis) to push food toward the stomach.

27. Stomach: • Large muscular bag. • Chemically digests food with acids and enzymes (pepsin) that break down protein. • Mechanically breaks down bolus into small particles and mixes them with stomach enzymes to create chyme.

28. Stores food and slowly releases it into the small intestine. • Some cells secrete a mucus layer to protect the stomach lining from the acid. • If the mucus layer is damaged, acid can burn the stomach tissue and cause an ulcer.

30. Stomach ulcer

31. Small intestine: • The final part of digestion happens here. This is the longest part of the digestive tract. • 6 meters long, 2.5 centimeters wide

32. Duodenum: First section of the small intestine. Where most digestion occurs. • Mucus protects the lining from acidic chyme • Enzymes break down carbohydrates and proteins. • Liver and pancreas add other enzymes and chemicals. • Peristalsis mixes chyme with other chemicals and pushes the chyme along.

34. Liver: • Makes bile, which breaks down fats. • Gallbladder: Stores bile and “squirts” it into duodenum through duct as needed.

36. Pancreas: • Produces enzymes that digest proteins, carbohydrates, fats, DNA, and RNA. • Secretes a basic (alkaline) fluid that neutralizes acid in the chyme.

38. 21.3 Absorption of Food • Absorption: The process of moving food through the intestinal wall into the bloodstream through diffusion and active transport. • Food must be filtered through the cell membrane to get into the blood.

39. Small intestine: • The only place where nutrients from food are absorbed. • The inner surface has folds and finger-like projections (villi) that increase surface area, and the cells themselves have tiny folds on their surfaces (microvilli). In each villusis a small artery, a small vein, capillaries, and a lymph vessel.

41. How absorption works: • Nutrients (sugars, short proteins, some vitamins and minerals, simple fatty acids) pass through intestinal cells and are absorbed by capillaries.

42. Fats and fat-soluble vitamins are absorbed by the lymph vessel in villi, move through the lymphatic system and enter the blood in the heart to be carried to the body cells.

44. Nutrients in the body • Cells break down some food molecules to release energy. • Molecules are converted to glucose (main energy source), which is broken down during cellular respiration. • The energy is stored in ATP.

45. Other nutrients are used as building blocks. • Amino acids build proteins. • Nucleic acids build DNA and RNA. • Unused energy is stored in fats.

46. Large intestine: • Wider and shorter than small intestine. • Chyme here contains only indigestible materials and water. • Most of the water is reabsorbed. • Prevents dehydration. • Bacteria live in the large intestine. • Digest cellulose (Gives off gas!) • Secrete vitamin K, thiamine (B1), and niacin (B3) that are absorbed by the large intestine.

48. 21.4 What is excretion? • Excretion: The process of waste removal. • Solids, liquids, and gases.

49. Solid wastes: • Feces: Solid material left over after digestion and absorption of food. • Contains water, dead bacteria, bile, salts, and indigestible material (cellulose). • Cellulose: Humans don’t make the enzymes necessary to digest it. • The fibers absorb water, which makes the feces softer and easier to excrete.

50. Liquid wastes: • Urine and sweat. Contain more than 90 percent water. • Amino acids that are not used immediately for building are broken down for energy. • Nitrogen released as ammonia. • Ammonia converted to less toxic urea. • Kidneys filter urea out of blood.