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Food Processing in 4 Steps: Ingestion, Digestion, Absorption, Elimination

Learn about the process of food processing and digestion, including ingestion, mechanical and chemical breakdown, absorption, and elimination. Explore different modes of ingestion and types of digestive tracts. Understand adaptation to diet in mammals and the human digestive system.

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Food Processing in 4 Steps: Ingestion, Digestion, Absorption, Elimination

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  1. CHAPTER 34 DIGESTION & NUTRITION

  2. I. Food Processing in 4 steps: A. Ingestion 1. Act of eating; taking in food B. Digestion 1. Breaking down of food into molecules small enough for the body, or cells, to absorb 2. Need to be broken down to: a. To allow them to enter cells b. Make polymers from monomers for own body

  3. 3. Digestion occurs in two steps: a. Mechanical breakdown  Food broken into small pieces b. Chemical breakdown  Hydrolysis breaks down chemical bonds in polymers by adding water  Catalyzed by enzymes

  4. C. Absorption 1. Cells in lining of digestive tract take up small nutrient molecules 2. Molecules travel in blood to other body cells D. Elimination 1. Undigested material passes out of digestive tract

  5. III. Types of Digestion A. Intracellular Digestion 1. Single celled-organisms, like Paramecium, have food vacuoles in cell to digest food 2. Simple invertebrates, like sponges, also digest food within own cells B. Extracellular Digestion 1. Have a compartment in body in which food is digested. 2.  Food is NOT digested inside of cells, but outside of them.

  6. IV. Various Modes of Ingestion A. Some organisms absorb nutrients through their body surfaces 1. Tapeworms, etc. B. Ingestive feeders 1. Ingest food through a mouth C. Three kinds of ingestive feeders: 1. Herbivores - plant-eaters 2. Carnivores - eat other animals 3. Omnivores - eat both plants & animals

  7. D. Ways of Ingesting, or Eating, Food 1. Continuous Feeders ♣ Also called filter feeders ♣ Constantly bring in water from outside ♣ Somehow capture particles in the water, including algae, protozoans, minute invertebrates, in gills or other structures ♣ Examples: clams, fanworms, baleen whales

  8. Discontinuous Feeder Continuous Feeder

  9. 2. Discontinuous Feeders ♣ Take food into mouth ♣ Enters some kind of storage area ♣ Don’t need to eat continuously since they can take in larger prey ♣ Examples: most animals

  10. Discontinuous Feeder Continuous Feeder

  11. V. Types of Digestive Tracts A. Incomplete Digestive Tracts 1. Digestive system has a single opening, the mouth. Acts as both entrance and exit. 2. Digestive enzymes in tract allow some extracellular digestion 3. Digestion is finished by cells that line the tract 4. Examples: a. Hydra who use stingers on tentacles to capture prey b. Planaria, carnivorous flatworms

  12. Incomplete Digestive Tract of a Planarian

  13. B.Complete Digestive Tract or Alimentary Canal 1. Is a tube between 2 openings: a. mouth b. anus 2. Food moves in one direction 3. Regions can be specialized to carry out functions in sequence: a. Ingestion b.Digestion& thenc. Absorption of nutrients

  14. Complete Digestive Tract of an Earthworm

  15. E. Specialized Organs in Earthworm 1. Pharynx = throat 2. Esophagus = food tube 3. Crop a.Pouch-like organ in which food is softened & stored temporarily 4. Gizzard a. Stores & grinds food b. Have grit or stones to help do this 5. Stomach a. Stores food temporarily b. Muscles help churn food

  16. 6. Intestine a. Region of chemical digestion b. Where nutrients are absorbed 7. Anus a. Opening through which undigested materials are expelled

  17. VI. Adaptation to Diet in Mammals A. Dentition (Teeth Anatomy) 1. Dentition varies according to mode of nutrition 2.Grazers (herbivores) a. Horses have:  Sharp even incisors used for clipping blades of grass.  Large flat premolars & molars for grinding & crushing grass b. Ruminants (cattle, sheep, deer)  Quickly swallow food into four- chambered stomach  Bacteria digest into cud  Regurgitate & chew food again

  18. Dentition Among Mammals

  19. 3. Carnivores a. Cats & dogs have:  Pointed incisors & enlarged canine teeth to tear off pieces of meat small enough to be swallowed b. Toothed whales & dolphins:  Swallow food whole  Have many conical teeth to catch & grasp slippery prey 4. Omnivores (humans, raccoon, rat, bear) a. Have variety of teeth for eating both plant & animal food: incisors, canines, premolars, molars

  20. Dentition Among Mammals

  21. The Human Digestive Tract

  22. IV. Human Digestive System

  23. A. Oral cavity 1. Teeth– mechanical breakup a. incisors - biting b. canines – tearing c. premolars & molars - grinding 2. Saliva – dissolves & lubricates a. Contains enzyme, salivary amylase, and an anti-microbial chemical called thiocyanate 3. Tongue – manipulates food into a bolus (mass) & pushes into pharynx

  24. Swallowing

  25. B. Pharynx 1. Air and food passageway C. Esophagus 1. Tube from pharynx to stomach a. Food moves down by a process called peristalsis ● Circular muscles push food 2. There is a ring of muscle called the cardiac sphincter at entrance to stomach a. Stays closed except when food is arriving.

  26. Peristalsis in the Digestive Tract

  27. D. Stomach 1. A large muscular sac, J-shaped 2. Functions as storage organ 3. Composed of three layers: epithelium, muscle, connective tissue 4. Capable of varied movements that help in mechanical digestion 5. Gastric glands of epithelium secrete: a. mucous – protects lining b. gastric juice – hydrochloric acid + digestive enzymes 6. Mixing of food with acid creates thick creamy solution called chyme

  28. Anatomy of the Stomach

  29. E. Small Intestine 1. Where most digestion & absorption occurs 2. Long & coiled (up to 23 feet) 3. Pyloric sphincterbetween stomach and intestine lets food enter 4. First part is called the duodenum. This is where the digestive enzymes are released by epithelium of small intestine & arrive from the pancreas. 5. Herbivore intestines much longer than those of carnivores 6. Adaptations to increase area for absorption of nutrients: Long length, folds, villi & microvilli, and lacteals (absorb glycerol & fatty acids)

  30. Anatomy of Small Intestine Folds, villi, microvilli help to greatly increase surface area for absorption. Capillaries absorb sugars & amino acids; lacteals absorb fatty acids

  31. Digestive & Absorption of Nutrients

  32. F. Large Intestine(Colon) 1. Consists of ascending, transverse and descending colon 2. Appendix hangs off of it 3. Functions in reabsorption of water a. Peristalsis too fast – diarrhea b. Too slow – constipation c. Roughage (fiber) – needed to stimulate peristalsis G. Rectum 1. Storage chamber for feces 2. Waste eliminated through anus.

  33. Liver, Gallbladder, and Pancreas

  34. Liver also functions to: Maintain blood glucose at appropriate levels by storing & breaking down glycogen. 2. May also convert amino acids to glucose.

  35. Nutrition I. 3 Basic nutritional needs of all animals: A. Fuel to power activities B. Organic raw materials to make the body’s own molecules C. Essential nutrients the animal cannot make for itself but must obtain in prefabricated form

  36. Food Guide Pyramid

  37. II. Importance of Carbohydrates A.Energy for cells B. Recommendations: 1. Eat complex carbohydrates like whole grains  These are digested more slowly & contain fiber  Insoluble fiber (wheat bran) has laxative effect; may guard against colon cancer  Soluble fiber (oat bran) binds with bile & cholesterol & prevents them from being absorbed

  38. 2. Eat minimal amount of simple sugars  These enter bloodstream almost immediately  These foods have a high glycemic index. Cause blood glucose levels to rise quickly & dramatically. Over extended period of time this might lead to type 2 diabetes.

  39. II. Importance of Proteins A. Humans cannot make 9 of the 20 amino acids needed to synthesize proteins. Called essential amino acids 1. We must eat these on a regular basis since the body does not store them B. Easiest way to get them is to eat meat and animal by-products like milk, eggs, & cheese 1. Vegetarians need to eat variety of foods that combined contain all the essential amino acids

  40. III. Importance of Lipids A.Functions of Fat: 1. Store excess energy 2. Insulate against cold 3. Helps to have healthy immune system (in moderate amounts) 4. Proper levels of fat:  Women- ~ 20-25% is normal  Men- ~ 15-19% is normal

  41. B. How Do We Make Fat? 1. Combine fatty acids with glycerol 2. We can make most of the fatty acids. Those we can’t make are called essential fatty acids.  We must eat these

  42. C. Good Fat versus Bad Fat 1. Saturated Fats = “bad”  Usually of animal origin & solid at room temp: meat, butter, milk  Associated with heart disease 2. Unsaturated Fats = “good”  Usually of plant origin: liquid oils  Polyunsaturated oils are the best & have the essential fatty acids we need (olive & canola oil)  Omega-3 fatty acids thought to protect against heart disease (found in cold water fishes: salmon, sardines & trout)

  43. IV. Importance of Vitamins A. Organic nutrients that body can’t manufacture & are required in much smaller quantities than essential amino acids 1. Many serve as coenzymes a. They have catalytic functions B. Deficiencies cause serious problems C. Fat-soluble vitamins stay in body 1. Can overdose on them D. Excess water-soluble vitamins will be excreted from body

  44. V. Minerals A. Chemical elements other than C,H,O,N that are essential for body functioning. 1. Acquired in our diet B. We require large amounts of: 1. Ca, P, S, Mg, Na, K, Cl 2. In U.S. we get ~ 10X the amount of Na than we truly need by consuming salt in our diet C. We require smaller amounts of: 1. Fe, F, Zn, Cu, Co, Se, Mo, & I

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