1. The Human Body: The Digestive System Textbook Chapter 35 Review Book Topic 1

2. Function Ingest (eat) food Breaks food down to absorb nutrients Eliminates what cannot be digested as waste

4. Ingestion Mechanical digestion – involves physical breakdown of food into smaller pieces Teeth and tongue in the mouth Smooth muscles in the stomach Smooth muscles in the small intestines

5. Chemical digestion – enzymes are used to break down large molecules into smaller molecules that can be absorbed by cells Ex. Amylase – enzyme found in saliva which causes the breakdown of starches into sugars

7. Esophagus As the tongue pushes chewed food to the back of the mouth, the swallowing reflex is stimulated Esophagus connects the mouth to the stomach

9. Lined with smooth muscles that contract rhythmically to move food through the digestive system in a process called peristalsis Continues throughout the digestive tract Not even affected by gravity….you could still digest food upside down!

11. When a person swallows, the epiglottis covers the trachea (windpipe) If food enters the windpipe, choking occurs

12. Stomach A sphincter, a circular muscle, controls the movement of food from the esophagus into the stomach Stomach walls are composed of three layers of smooth muscle Involved in mechanical digestion and chemical digestion

14. Very acidic environment Gastric glands secrete an acidic solution at pH 2 Any leakage of stomach acid through the sphincter muscles can cause acid to reach the esophagus, causing heartburn

15. Pepsin – enzyme involved in the chemical digestion of proteins in the stomach Cells in the lining of the stomach secrete mucus to help prevent stomach acid from digesting the stomach’s cells Some substances like alcohol and aspirin are absorbed by stomach cells (but most absorption occurs in the small intestine)

16. When empty, stomach capacity is about 50 mL When full, it can expand to 2 – 4 L Muscular stomach walls contract and push food farther along the digestive tract Empties through another sphincter into the small intestine

17. Small Intestine 7 m in length Longest part of the digestive system Small intestine because the diameter is 2.5 cm compared to the diameter of the large intestine at 6.5 cm Smooth muscular walls continue the process of mechanical digestion and peristalsis

19. Chemical digestion is completed by accessory organs Pancreas Produces enzymes that digest carbohydrates, proteins, and fats Produces hormones Secretes an basic solution to raise the pH in the small intestine to pH 7 (neutral) for the optimum environment for enzyme action in the small intestine

20. Liver Largest internal organ of the body Produces bile which breaks down fats About 1 L of bile is produced each day and any excess is stored in the gall bladder Gall bladder Stores excess bile Releases bile into the small intestine when needed

22. Nutrients from food are absorbed from the small intestine into the bloodstream through villi Fingerlike projections Increase the surface area of the small intestine Gives the small intestine as much absorption room as a tennis court!

26. When digestion is complete, any remaining food, in the form of chyme moves into the large intestine Chyme is a semi-liquid solution composed of materials that cannot be digested or absorbed by the small intestine

27. Large Intestine End portion of the digestive tract 1.5 m long Includes the colon, rectum and appendix Colon normally contains bacteria which produce vitamin K and some B vitamins Primary function is to absorb water from chyme

29. Indigestible material becomes more solid as water is absorbed, forming feces Peristalsis continues to move feces to the rectum Walls of the rectum to stretch initiating a reflex Final sphincter muscle to relaxes, eliminating the feces from the body through the anus

30. Digestive StructurePrimary FunctionTime Food in Structure MouthMechanical and chemical digestion 5-30 seconds EsophagusTransport (swallowing) 10 seconds StomachMechanical and chemical digestion 2-24 hours Small IntestineMechanical and chemical digestion 3-4 hours Large IntestineWater absorption18 hours – 2 days

31. Digestive System BrainPop

32. Nutrition Nutrition – process by which a person takes in and uses food Food supplies building blocks and energy needed by the body to maintain body mass Daily input of energy from food should equal the amount of energy a person uses daily

33. Calorie – unit used to measure the energy content of food 1 calorie is the amount of heat needed to raise the temperature of 1 mL of water by 1°C Can be found by burning the food and converting its stored energy to heat To lose weight, more calories must be used than consumed

34. Carbohydrate Ex. cereal, pasta, potatoes, strawberries, rice Broken down into simple sugars Stored in the liver in the form of glycogen Cellulose – a plant starch – cannot be digested but is required by humans to “flush” out and keep the digestive tract clean (also known as fiber)

35. Fats Essential for your diet in proper amounts The most concentrated energy source available to the body Protect internal organs Maintain homeostasis by providing energy, storing and transporting certain vitamins

36. Not all fats are beneficial Saturated (solids) Ex. Meats, cheeses, dairy “Unhealthy” Can result in high blood pressure or heart problems Unsaturated (liquids) Ex. Plants “Healthy”

37. Digested in small intestine Broken down into fatty acids and glycerol

38. Proteins Basic structural components of all cells Made up of amino acids Absorb into the blood and are “rebuilt” when they enter body cells 20 amino acids 8 of these we cannot make in our body and must obtain them from our food

39. Form enzymes, hormones, neurotransmitters, membrane receptors Ex. Animal byproducts: meat, fish, poultry, eggs, dairy Ex: Plants (only cover some of the essential amino acids needed…ex. beans + rice)

40. Food Pyramid Changed in 2005 by the Department of Agriculture Shows which foods and the amount of these foods is right for your diet

41. Old Food Pyramid

42. Modern Food Pyramid

43. Vitamins and Minerals Vitamins – organic compounds needed in small amounts for metabolic activities Help enzymes function Obtained by your diet, cannot be made in large enough quantities by your body Some can be stored in your liver but many cannot

44. Minerals – inorganic compounds used as building materials an involved in some metabolic functions Taking over the recommended daily amount of vitamins or minerals can be dangerous

45. Nutrition Labels Provided on commercially packaged foods Based on a diet of 2000 calories a day Required information: Name of food Net weight or volume Manufacturer information Ingredients Nutrient content