Human Digestive System

1. Human Digestive System

2. Two types of food components Nutrients: substances that can be digested (if necessary), absorbed and used within the body Roughage (fiber): a) substances that cannot be digested or absorbed b) primarily cellulose from plant cell walls

3. Roughage Benefits • stimulates muscle contractions (peristalsis) that move food through the digestive system • prevent constipation • reduce risk of colon cancer • reduce the amount of cholesterol in the blood • can help you lose weight (suppress appetite without adding calories)

4. Sources of roughage • Fruits, vegetables, grains and other “natural” foods that come from plants are good sources • “Processed” foods from plant sources often have little or no roughage Example: table sugar, “instant rice”, cereals that are not “whole grain”, snacks like chips, cheese doodles, candy bars etc. 3) “low carbohydrate diets” may contain too little fiber

5. Three Uses for Nutrients • Energy Sources • Structural Material for growth and tissue maintenance 3) Regulation of Body Functions

6. Six Important Nutrients 1) Water 2) Minerals 3) Vitamins 4) Proteins 5) Carbohydrates 6) Lipids (fats)

8. 1. Water 1) most abundant substance in any organism 2) importance in human body: a) solvent & transport medium b) stimulates chemical reactions c) regulation of body temperature d) required for digestion (hydrolysis) e) dilution of toxic waste products f) helps immune system

9. Problems associated with dehydration 1) headaches 2) impairs immune system 3) increased thirst 4) lack of energy 5) hyperthermia (elevated body temp.)

10. How much fluid should you drink each day • 1. 9 liters of fluids • 64 ounces (8 eight ounce glasses) • Half gallon

11. Symptoms of Dehydration • Thirst • Dark Urine • Dry mouth

12. 2. Minerals Simple inorganic substances like: • Calcium (Ca) • Phosphorous(P) • Iron (Fe) • Sodium (Na) • Potassium (K) • Iodine (I)

14. 3. Vitamins • Small organic substances which regulate body processes b) Most are “coenzymes” (they assist enzymes in controlling reactions)

16. Proteins 1. Used for: a) structural material b) enzymes (catalyze reactions) c) hormones (chemical messengers) d) antibodies (fight disease) • Complete proteins: a) contain all of the 8 essential amino acids that must be in your diet. b) proteins from animals are generally complete

17. Carbohydrates • Sugars and starches • Primary source of energy 3. Should provide about 2/3 of the calories in your diet

18. Lipids (fats, oils, wax) Used for: a) energy storage (contain about twice the calories per gram of carbohydrates or protein) b) structural material (cell membranes) c) insulation d) padding e) production of steroid hormones

19. come mainly from animals easily converted to cholesterol 3. increase chances of: heart attack, high blood pressure and stroke come mainly from plants less likely to raise cholesterol 3. fewer health risks Saturated Fats vs. Unsaturated

20. Problems with American Diet 1. Too many: calories, fats, simple sugars, saturated fats and sodium 2. Not enough: variety, calcium, roughage, fruits & vegetables

21. Problems Associated with Obesity 1. Cardiovascular diseases • Heart disease, high blood pressure, stroke • Arthritis • Diabetes 4. Increased Cancer risk

22. Energy Needs 1. young males need about 2800 calories per day 2. young females need about 2200 calories per day decrease with age 3. increase with physical activity

24. Eating Disorders 1. Anorexia Nervosa a) excessive concern about gaining weight b) victims starve themselves 2. Bulimia (binge & purge syndrome) overeating followed by self induced vomiting, fasting or use of laxatives

25. Digestive Terms 1. Ingestion to take in food 2. Egestion to remove undigested materials from the digestive system (egestion is not excretion) 3. Digestion the breakdown of food so that it can be absorbed 4. Peristalsis muscle contractions that move food through digestive organs

26. Peristalsis

27. peristalsis movie

28. Two Types of Digestion 1. Mechanical a) physical breakdown into smaller pieces b) chewing, grinding and dissolving increases the surface area for faster chemical digestion

29. 2. Chemical Digestion a) “hydrolysis” of large molecules into their building blocks by enzymes b) Large molecule + H2O Small Molecules c) Water, minerals and vitamins do not require chemical digestion

32. Human Digestive Organs

33. Two types of digestive organs 1. Organs of the Alimentary Canal (GI Tract) form the passageway that food travels through include: mouth pharynx esophagus stomach small intestine large intestine (colon) anus

34. 2. Accessory Organs Secrete fluids into the alimentary canal Include: a) salivary glands b) liver c) gall bladder d) pancreas

35. The Mouth Chewing is a form of : mechanical digestion Saliva: a) helps food dissolve so it can be tasted b) contains pytalin (salivary amylase), which: - converts starch into sugar ( chem digestion) Tongue: a) aids in swallowing b) contains 4 types of taste buds: sweet, sour, bitter & salty

36. Pharynx a) the area behind your mouth b) during swallowing, food is kept out of the trachea (windpipe) by the: epiglottis How can you assist someone who has food caught in the pharynx?

37. Esophagus • Carries food from the pharynx to the stomach • Involves wave like muscle contractions called peristalsis c) A ring like muscle called the lower esophageal sphincter: • keeps stomach acid out of the esophagus d) Heartburn: irritation of the esophagus by stomach acid

38. The Stomach • J shaped sac on the left side of your body • Contains 3 layers of muscle which grind food and mix it with “gastric juice” • Pyloric sphincter keeps food out of small intestine until it’s converted to a liquid

39. Gastric Juice Fluid secreted by stomach which contains: a) pepsin (gastric protease) a protein digesting enzyme b) hydrochloric acid (HCl) -kills most bacteria -helps food dissolve -provides the low pH -that pepsin needs c) Peptic ulcer : an irritation of stomach or small intestine caused by gastric juice

40. The Small Intestine • 6.5 meters (20ft) long and 2.5 cm (1 in.) thick • Most important digestive organ • Only organ where all types of nutrients can be digested • Over 90% of nutrient absorption occurs in SI • Secretes a basic fluid called intestinal juice which neutralizes stomach acid • Produces hormones that signal accessory organs to release their fluids

41. The Digestive System Page

42. Ideal pH’s for digestion: • in stomach it’s about 3 (provided by Hydrochloric Acid) • in small intestine it’s 8-9 (provided by intestinal & pancreatic juice)

43. Villi a) bumps in small intestine that increase surface area for absorption b) contain digestive enzymes on their surface c) most nutrients are absorbed into capillaries w/in villi d) fats and non-polar vitamins are absorbed into small lymph vessels called “lacteals”

45. Large Intestine (Colon) a) includes: ascending,transverse & descending colon, rectum and anus b) no digestive enzymes c) absorbs water from wastes d) eliminates wastes (feces) which consist of roughage & bacteria • E. coli bacteria live in colon, aid digestion and produce vitamins f) appendix –vestigial sac near ascending colon

46. Accessory organs(Organs that Secrete Into SI) 1. Pancreas -secretes all kinds of digestive enzymes -pancreatic juice is basic (high pH) Secretes insulin to regulate blood sugar levels

47. 2. Liver (largest internal organ) a) secretes “bile” into SI b) bile makes lipids dissolve in water, a process called emulsification c) emulsification allows fats to mix with lipases and is a form of mechanical digestion

48. 3. Gall Bladder a) stores bile that was produced in the liver b) gallstones: crystallized deposits of cholesterol which can block the flow of bile

49. Other Functions of Liver • Produce glycogen from glucose and store it when blood sugar is high • Breakdown glycogen to release glucose when blood sugar is low • Store vitamins and iron • Remove old red blood cells • Destroy harmful substances in bloodstream • Break down alcohol (about 1 oz. per hour)

50. Disorders of the Digestive system