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The Digestive System

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  1. The Digestive System

  2. Nutrients What is in the food you eat?

  3. Energy nutrients • Energy nutrients provide fuel for the body. This is measured in calories.

  4. Carbohydrates • 55-60% of diet should come from carbohydrates • 4 calories per gram • Primary food sources are grains, fruits, vegetables.

  5. Proteins • 10-15% of calories should come from Protein • 4 calories per gram • Best sources are meats and dairy, but plants (beans, nuts, etc.) have some of the amino acids that make up proteins

  6. Fats • Should comprise 25-30% of your diet • 9 calories per gram • Good sources; red meats, butter, oils, cheese, etc. • Needed for skin health, hormone production, and cell membrane integrity.

  7. Non-energy nutrients (no calories) Water, vitamins, and minerals- provide no fuel for energy, but are necessary in the chemical reactions needed to release energy and build tissues.

  8. Water. • Makes up approximately 65% of your body weight. • Needed to perform the chemical reactions and regulate body temperature. • Most important

  9. Vitamins • A- meats, milk, carrots • B- (B1, B2, B12, riboflavin, niacin, etc) vegetables, fruit, grains • C- citrus fruits • D-fortified milk, sunlight • E- fish • K- made by bacteria in your intestines

  10. Minerals- plants absorb from soil Iron- red meat, plants (for blood cells) Calcium and phosphorus – milk (bone health) Sodium- salts Potassium – bannanas Chloride- salts Many more trace minerals (only need a small amount)

  11. Calorie needs • The average adult needs about 2,000 calories per day to supply the energy needs and provide adequate amounts of vitamins and minerals for proper functioning. • The food guide pyramid amounts and categories insure that all necessary nutrients will be consumed.

  12. Pg 512

  13. Exceptions • Caloric needs vary depending on the size of the person and their activity levels. • Larger persons need more calories • Very active persons need more calories • Regardless of the calories, you must maintain the proper balance of nutrients.

  14. RDA (recommended daily allowance) • The United States Food and Drug Administration sets the minimum amount of each nutrient that a person should get each day to maintain their optimal health. This is called the recommended daily allowance.

  15. Weight gain or loss • Weight is a tricky word. We should be less concerned about weight and more concerned about body composition. What we want to do is keep body Fat levels at the proper percentage. • See chart on next slide for Proper body fat levels.

  16. Weight facts • Muscle weighs more than fat • 1 pound of body fat is 3,500 calories • Healthy weight (fat) loss is 1-2 pounds per week. • If you are losing more than 2 pounds per week, you are probably losing water weight, not fat. • To lose 1 pound of body fat per week, either increase activity to burn 500 more calories per day or eat 500 less calories per day.

  17. Eating disorders • Bulimia- a person eats a normal amount, but then throws it back up before it completes digestion. • Anorexia Nervosa- a person starves themselves to the point that their body starts to consume their own muscle tissue (from skeletal, cardiac, and smooth) to supply the brain with it’s energy needs.

  18. The digestive process begins • The process of digestion occurs in stages and at different locations throughout the alimentary canal. You should be able to trace the process from start to finish and explain the role of each part during the process.

  19. Mouth (5-30 seconds) • Mechanical digestion- chewing breaks the food down into smaller particles that does not change the substance of the food. This makes greater surface area for the enzymes to work on. • Chemical digestion- food mixes with saliva, which contains enzymes that chemically changes carbohydrates into sugars.

  20. Mechanical digestion • Mechanical digestion begins in the mouth where the food is chewed into smaller pieces without changing the substance.

  21. Chemical digestion • Chemical digestion of carbohydrates begins in the mouth when enzymes in saliva start to change the food into base substances (sugars)

  22. Pharynx (throat) • When you swallow food, the tongue moves the food to the back of the Pharynx. The epiglottis covers the trachea (windpipe) to keep the food out of the lungs and directs the food into the esophagus.

  23. To the Stomach  Esophagus (10 seconds) • Swallowed food passes the trachea as the epiglotis covers the top of the trachea and directs food into the esophagus. Muscle contractions, called peristalsis, carry the food to the stomach. This takes about 10 seconds.

  24. Stomach (3 hours) The stomach is a J shaped organ lined with mucosal cells. It receives the food, mixes it with stomach acids and mashes the food into a paste called chyme. Then it pushes the food into the small intestine.

  25. Mashing and soaking in the stomach • Food is further broken down by strong acids (chemical) and enzymes as it is mashed (mechanical) into a paste in the stomach.

  26. Mucosal cells • Produce mucous inside the stomach to protect the stomach lining from damage by the strong stomach acids.

  27. Chemicals / enzymes /acid • The process of chemical digestion requires chemicals that break down the bonds of foods. Different chemicals work on different nutrient types. (some work on all) Examples: • Hydrochloric acid in the stomach all • Bile in liver stored in gall bladder fats • Saliva  salivary glands  carbohydrates • Pancreatic enzymes  pancreas proteins, fats

  28. Final digestion • Once the food has been dissolved and mashed it is time to absorb the nutrients into the blood to deliver to cells and to eliminate the waste material.

  29. Small Intestine (10-12 hours) • Upper part- mix food paste (chyme) with pancreatic enzymes to break lipids and proteins into small, absorbable particles • Food moves through the 23 feet of the small intestine while the villi absorb the broken down nutrients • Indigestible & unabsorbable material (such as fiber) is moved into the large intestine

  30. Small intestine

  31. Villi

  32. Large Intestine (3-4 hours) • Reabsorbs water, vitamins and prepares the undigested material for elimination from the body • Rectum stores the prepared waste material • Anus – opening through which waste is eliminated

  33. Large intestine

  34. Accessory organs • Food does not enter these organs. They produce or secrete chemicals into the system to help in the chemical digestion process.

  35. Liver • Food does not enter the liver, gall bladder, or the pancreas, but they each play an important roll in the process of digestion. • Produces bile for the breakdown of fat • Also acts to filter toxins and neutralize them

  36. Gall bladder • Stores bile until it is secreted into the intestine

  37. Pancreas • Produces enzymes that complete the breakdown of fats and proteins into individual lipid and amino acid molecules. • Also functions as an endocrine gland producing insulin and other hormones. (double gland)

  38. Appendix • Composed primarily of lymphatic tissue that helps development of the immune response.