Digestion!
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Digestion!

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Digestion! Presentation Transcript

  • 1. Unit C1-2: Human Biology (Digestive System)
    • Students who have fully met the prescribed learning outcomes (PLO’s) are able to:
    • C1. Analyze the functional inter-relationships of the structures of the digestive system.
      • Identify and give a function for each of the following:
    • -mouth -duodenum
    • -tongue -liver
    • -teeth -gall bladder
    • -salivary glands -pancreas
    • -pharynx -small intestine
    • -epiglottis -large intestine (colon)
    • -esophagus -appendix
    • -cardiac sphincter -rectum
    • -stomach -anus
    • -pyloric sphincter
  • 2. Digestion PLO’s
      • Describe swallowing and peristalsis.
      • Identify the pancreas as the source gland for insulin, and describe the function of insulin in maintaining blood sugar levels.
      • List at least six major functions of the liver.
      • Explain the role of bile in the emulsification of fats.
  • 3. Digestion PLO’s
      • Describe how the small intestine is specialized for chemical and physical digestion and absorption.
      • Describe the structure of the villus, including microvilli, and explain the functions of the capillaries and lacteals within it.
      • Describe the functions of anaerobic bacteria in the colon.
      • Demonstrate the correct use of the dissection microscope to examine the various structures of the digestive system .
  • 4. Digestion PLO’s (Last set!)
      • Describe the role of sodium bicarbonate in pancreatic juice.
      • Describe the role of hydrochloric acid (HCl) in gastric juice.
      • Describe the role of mucus in gastric juice.
      • Describe the importance of the pH level in various regions of the digestive tract.
  • 5. C1 – Organs and Their Functions :
  • 6. First off…..the MOUTH!!
  • 7. Mouth…where it all begins
    • Receives food to be broken down physically (teeth)and chemically .
    • Location of starch digestion/first place of chemical digestion of starch.
    • Saliva in mouth provides optimal pH 7 for salivary amylase.
  • 8. Tongue
    • Forms chewed food into a bolus (ball of food) before swallowing.
    • Initiates swallowing.
  • 9. Teeth! Chomp chomp….
    • Mechanical/physical breakdown of food (mastication).
  • 10. Salivary Glands
    • Three pairs of glands that secrete saliva into the mouth via ducts.
    • Produces saliva containing water, mucus , salivary amylase and buffers which, lubricate food, and breakdown starch into maltose. (It also contains the enzyme, lysozyme that lyses oral bacteria).
  • 11. Salivary Glands
  • 12. Pharynx
    • A region between the mouth, esophagus, and trachea.
    • Passageway for food, water, air, and for the reflex action of swallowing as it enters the esophagus.
  • 13. Epiglottis…so you don’t choke!
    • A flap of tissue that covers the glottis (opening of the trachea).
    • Prevents food from entering the trachea when swallowing.
  • 14. Esophagus
    • Transfers the bolus from the mouth to the stomach by peristalsis (rhythmic smooth muscle contractions).
    • Secretes mucus for lubrication
  • 15. Cardiac Sphincter
    • Circular muscle at the junction of the esophagus and stomach.
    • Relaxation of sphincter allows bolus to enter stomach and contraction prevents stomach chyme from re-entering the esophagus.
  • 16. Stomach
    • J-shaped muscular and glandular organ on the left side of body below the diaphragm.
    • Stomach wall contains deep folds ( rugae ) which provide a greater surface area for food and fluids.
    • Storage of food
  • 17. Stomach continued
    • Mechanical churning of food into chyme by smooth muscle fibres.
    • Secrete mucus for protection and lubrication by goblet cells.
    • Secretes HCl and pepsinogen (inactive form of pepsin ) by gastric glands.
    • Secretes gastric juice produced by gastric glands containing H 2 O, HCl, pepsinogen (pepsin), and mucus. HCl provides optimal pH 2-3 for pepsin.
  • 18. Stomach
    • First place of chemical digestion of proteins .
    • Secretes gastrin (hormone), which releases more gastric juice from gastric glands.
  • 19. Pyloric Sphincter
    • A circular ring of muscle at the junction of the stomach and duodenum.
    • Relaxation of the sphincter allows acid chyme to enter the duodenum,
      • i.e. controls the amount of chyme entering the duodenum and contraction keeps chyme within the stomach.
  • 20. Duodenum
    • First 30cm of the small intestine.
    • Receives acid chyme from stomach, pancreatic juice from pancreas, and bile from gall bladder; peristalsis occurs here.
    • Bile begins its first emulsification of lipids here, i.e. lipids physically broken down into lipid droplets.
  • 21. Duodenum
  • 22. Duodenum Continued
    • Majority of chemical digestion (see below) and the first neutralization (via NaHCO 3 ) of acidic chyme occur here. NaHCO 3 provides optimal pH 8-9 for pancreatic amylase, lipase, trypsin, intestinal & pancreatic nuclease, peptidase and maltase.
  • 23. Enzymes at work
            • H 2 O
    • starch maltose
    • pancreatic amylases
    • H 2 O
    • maltose glucose
    • maltase
    • H 2 O
    • proteins peptides
    • trypsin
  • 24. More enzymes
    • H2O
    • peptides amino acids
    • peptidase
    • H2O
    • nucleic acids nucleotides
    • pancreatic & intestinal nucleases
    • H2O
    • lipid droplets glycerol &
    • lipase fatty acids
  • 25. Liver
    • Refer to major liver functions for specifics .
    • Accessory organ for digestion consisting of four lobes, located under the diaphragm.
    • Approximately 1.5kg in weight.
    • Highly vascularized.
    • Produces bile (bile salts) necessary for emulsifying lipids (thus increasing surface area for chemical digestion by lip ase ).
  • 26. Gall Bladder
    • Accessory organ for digestion.
    • Pear-shaped sac located in a depression on the underside of the liver.
    • Stores and concentrates bile from the liver and carries it to the duodenum via the bile duct.
  • 27. Pancreas
    • Refer to function of insulin for specifics .
    • Accessory organ for digestion.
    • Oblong gland, approximately 12.5cm, which lies behind the stomach and made up of clusters of glandular cells.
  • 28. Pancreas
    • Secretes pancreatic juice containing H 2 O, NaHCO 3 , pancreatic amylase , lipase , trypsin and pancreatic nuclease .
    • Secretes pancreatic juice for further digestion of starch, lipid droplets, proteins and nucleic acids, which is delivered to the duodenum via the pancreatic duct.
    • Neutralizes acid chyme by producing
    • NaHCO 3 .
    • Secretes enzymes for chemical digestion of all biological molecules.
  • 29. Small Intestine
    • Up to seven meters in length and 2.5cm in diameter.
    • Divided into three sections; the first 30 cm is the duodenum .
    • Walls of the small intestine are covered in villi (small finger-like projections), smooth muscle fibers, pits containing intestinal glands secreting enzymes, goblet cells secreting mucus, epithelial cells contain microvilli , and many folds which increase the surface area for chemical digestion and absorption.
  • 30. Small Intestine
  • 31. Small Intestine
    • Produces intestinal juice containing H 2 O, mucus, maltase , peptidase and intestinal nuclease .
    • Provides optimal pH 8-9 for intestinal nuclease, peptidase and maltase, pancreatic amylase and nuclease, lipase, trypsin.
    • Complete digestion of carbs, proteins, nucleic acids, and lipids.
  • 32. Enzymes at work
            • H 2 O
    • starch maltose
    • pancreatic amylases
    • H 2 O
    • maltose glucose
    • maltase
    • H 2 O
    • proteins peptides
    • trypsin
  • 33. More enzymes
    • H2O
    • peptides amino acids
    • peptidase
    • H2O
    • nucleic acids nucleotides
    • pancreatic & intestinal nucleases
    • H2O
    • lipid droplets glycerol &
    • lipase fatty acids
  • 34. Small Intestine Cont.
    • Absorption of all nutrients/monomers into the villi.
    • Receives acid chyme from stomach, secretions from the gall bladder, and pancreas.
    • Undigested material is transported to the large intestine by peristalsis .
    • Long length allows time for enzymatic reactions to occur and increases absorptive area for monomers/nutrients.
    • Increased surface area of intestinal cells by microvilli further increases absorption of monomers/nutrients.
  • 35. Appendix
    • Worm-like projection arising from the junction of the small and large intestine.
    • Vestigial (underdeveloped) organ with no known functions in humans, however, it may have a role in the lymphatic system.
  • 36. Large Intestine (colon)
    • Up to 1.5 meters long and 7.5 centimeters wide.
    • Contains a series of pouches that have a puckered appearance and also contains smooth muscle fibers for peristalsis .
    • Houses anaerobic bacteria called E. coli , which synthesizes vitamins B , and K, growth factors, amino acids, and further breaks down undigested materials by fermentation.
  • 37. Large Intestine
  • 38. Large Intestine (colon)
    • Absorption of H 2 O from feces and salts, e.g. high [solute] of the feces will cause watery feces/diarrhea (recall B10, hypertonic).
    • Secretes mucus for lubrication.
  • 39. Rectum
    • Last 20 cm of large intestine (colon),
    • controlled by a sphincter muscle.
    • Compacts/stores feces and opens into anus.
  • 40. Anus
    • Opening of rectum, surrounded by sphincter muscles.
    • Controls opening of rectum.
    • Elimination of feces (defecation) by relaxing sphincter muscles.
  • 41. Swallowing and Peristalsis
    • Swallowing is a reflex action (automatic ) triggered when the bolus is pushed upwards by the tongue against the soft palate and back towards the pharynx .
    • The larynx elevates, bends the epiglottis , which covers the glottis in the trachea, to prevent food from entering the lungs.
  • 42. Peristalsis
    • Peristalsis is the alternating contracting and relaxing of smooth muscles . It occurs in the esophagus moving the bolus to the stomach and provides movement of chyme in the small intestine and undigested material in the large intestine .
  • 43. Pancreas and Insulin
    • An accessory organ of digestion (exocrine gland), which produces pancreatic juice (H2O, NaHCO 3 , pancreatic amylase, lipase, trypsin, and pancreatic nuclease) and empties into the duodenum via pancreatic duct.
  • 44. Insulin
    • Also produces a hormone called insulin (from the islets of Langerhans) (endocrine gland) which is secreted into the bloodstream and has the following effects when the concentration of glucose in the blood/blood glucose is high :
    • i) Stimulates cells permeability to C 6 H 12 O 6 ;
    • stimulates liver, fat, and muscle cells to metabolize C 6 H 12 O 6 .
    • ii) Stimulates liver and muscle cells to store excess C 6 H 12 O 6 as glycogen .
    • iii) Promotes the buildup of fats and proteins,
    • and inhibits their use as an energy source.
  • 45. Six Major Functions of the Liver
    • Digestive System
    • Produces bile (which is stored in the gall bladder) to emulsify lipids.
    • Stores excess glucose as glycogen to maintain glucose levels.
    • Circulatory System
    • Produces blood proteins/plasma proteins from the amino acids (e.g. albumin, gamma-globulin, fibrinogen).
    • Detoxifies blood by removing alcohol, drugs, and other poisonous materials.
    • Converts Hb from worn out RBCs for the production of bile.
  • 46. Functions of Liver (5 and 6)
    • Excretory System
    • Produces urea from the breakdown of amino acids and excretes it as a N-waste.
    • Metabolizes ammonia (N-waste) to urea and excretes it in the urine.
  • 47. C2 – Enzymes and Digestive Reactions They Promote
    • Introduction
    • Enzymes are hydrolytic , that is, adding H 2 O breaks bonds.
    • 1.) Carbohydrates
    • (a) Salivary amylase , produced in the salivary glands; optimal pH 7 .
    • (b) Pancreatic amylase , produced in the pancreas; optimal pH 8-9 .
    • (c) Maltase , produced in the small intestine (intestinal glands); optimal pH 8-9 .
  • 48. Enzymes cont.
    • 2.) Proteins
    • (a) Pepsin , produced in the stomach (gastric glands); optimal pH 2-3 .
    • (b) Trypsin , produced in the pancreas; optimal pH 8-9 .
    • (c) Peptidase , produced in the small intestine (intestinal glands); optimal pH 8-9 .
    • NOTE : pepsin, inactive pepsinogen and trypsin are examples of enzymes called proteases .
  • 49. Enzymes cont.
    • 3.) Lipids
    • Lipase , produced in the pancreas; optimal pH 8-9 .
    • 4.) Nucleic acids/nucleotides
    • (a) Pancreatic nuclease , produced in the pancreas; optimal pH 8-9 .
    • (b) Intestinal nuclease , produced in the small intestine (intestinal glands); optimal pH 8-9 .
  • 50. C2 – Components of Digestive Secretions
    • NOTE: * = Enzyme.
    • Saliva
    • Produced by cells of three pairs of salivary glands located in the head, secreted into ducts which then enters the mouth.
    • Composed of:
      • H2O
      • Mucus
      • Buffers
      • Salivary amylase*
  • 51. Gastric Juice
    • Produced by gastric glands and mucus cells in the stomach.
    • Composed of:
      • H 2 O
      • Mucus
      • HCl
      • Pepsin*
  • 52. Pancreatic Juice
    • Produced by cells of the pancreas, travels to the pancreatic duct and then to the duodenum.
    • Composed of:
      • H 2 O
      • NaHCO 3
      • Pancreatic amylase*
      • Lipase*
      • Trypsin*
      • Pancreatic nuclease*
  • 53. Intestinal Juice
    • Produced by intestinal glands and mucus cells in the small intestine.
    • Composed of:
      • H 2 O
      • Mucus
      • Peptidase*
      • Maltase*
      • Intestinal nuclease*
  • 54. Summary of Enzymes and Chemicals/Molecules
    • 1.) Salivary amylase (mouth); breaks down starch + H 2 O  maltose.
    • 2.) Pancreatic amylase (pancreas to the duodenum); breaks down starch + H 2 O  maltose.
    • 3.) Maltas e (small intestine); breaks down maltose + H 2 O  glucose.
    Carbohydrates
  • 55. Proteins
    • 1.) Pepsin (stomach); breaks down proteins + H 2 O  peptides.
    • 2.) Trypsin (pancreas to the duodenum); breaks down protein + H 2 O  peptides.
    • 3.) Peptidase (small intestine); breaks down peptides + H 2 O  amino acids.
  • 56. Nucleic Acids
    • 1.) Pancreatic nuclease (pancreas); breaks down nucleic acids + H 2 O  nucleotides.
    • 2.) Intestinal nuclease (small intestine); breaks down nucleic acids + H 2 O  nucleotides.
  • 57. Lipids
    • 1.) Lipase (pancreas to the duodenum); breaks down lipid droplets + H 2 O  glycerol + fatty acids.
  • 58. Bile
    • (Produced in the liver, stored in the gall bladder, empties into the duodenum via ducts.)
    • NOT an enzyme; (a complex fluid containing H 2 O, electrolytes, bile acids, cholesterol, phospholipids and bilirubin.)
    • Emulsifies fats ( physical breakdown ) into fat/lipid droplets, which increases the surface area for chemical digestion by lipase.
  • 59. NaHCO 3 ( Sodium Bicarbonate)
    • Produced in the pancreas, empties into duodenum via ducts.
    • Neutralizes acid chyme from the stomach.
  • 60. HCl (Hydrochloric Acid)
    • Produced in the stomach.
    • Converts pepsinogen (inactive) to pepsin (active).
    • Kills bacteria and micro-organisms.
  • 61. H 2 O (water….in case you forgot)
    • Acts as a solvent.
    • Hydrolyzes enzymes.
    • Lubricates (aids in movement).
  • 62. Mucus
    • Produced in goblets cells of the stomach and cells of small and large intestine.
    • Lubricates the digestive tract.
    • Protection from acid chyme in stomach and small and large intestine.
  • 63. Cross-section of a Villus: (See following diagram)
    • Villus:
    • ‘ Finger-like’ projections found on the inner wall of the small intestine and extend into the intestinal lumen.
    • Villi (plural) increase the surface area for enzymatic reactions and absorption of monomers/nutrients in the small intestine.
  • 64.  
  • 65.
    • NOTE: The following are examples of how structures of the small intestine are related to its function.
    • The numerous villi increase the surface area for absorption of all nutrients.
    • The inside of each villus contains a capillary bed to absorb nutrients.
    • The inside of each villus contains a lacteal to absorb glycerol and fatty acids.
  • 66. More examples
    • The small intestine also contains microvilli (“brush border”). They are located on epithelial cells . This also increases the surface area for absorption of monomers/nutrients.
    • Epithelial cells are thin, moist and warm which speeds up diffusion/absorption.
    • Numerous mitochondria in epithelial cells provide ATP for active transport of nutrients.
  • 67. And more….
    • The walls of the small intestine contain smooth muscle cells that provide movement of chyme throughout the entire length.
    • This movement is known as peristalsis . Peristalsis also increases the surface area of the food.
    • The walls of the small intestine contain goblet cells that produce mucus , which aids in lubrication and movement.
  • 68. A few more examples
    • The walls of the small intestine also contain many folds , which increase the surfaces area for absorption of monomers/nutrients.
    • The length of the small intestine increases the surface are for absorption and chemical digestion of food.
  • 69.
    • Much of absorption includes active transport , but passive transport also occurs.
    • Each villus (and therefore microvillus) contains:
      • Epithelial cell s .
      • Mucus (goblet cells).
      • Lacteal (lymphatic vessel).
      • Capillary bed/network.
    • They allow for absorption of H 2 O, ions, minerals, and monomers .
  • 70. Processes of monomers and water entering intestinal epithelial cells
    • Lipids :
    • Glycerol and fatty acid monomers diffuse across the epithelial cells and then diffuse into the lacteal vessel .
    • These monomers will form triglycerides as they enter the lymphatic system  enters heart and general circulation.
  • 71. Carbs and Proteins
    • Glucose and amino acid monomers move by active transport into epithelial cells , and then diffuse into capillary bed / network .
    • Glucose and amino acid monomers then enter the bloodstream to the liver via hepatic portal vein , exits liver via hepatic vein to the heart, which then pumps C 6 H 12 O 6 and amino acids throughout the body.
    • Now the liver can store excess C 6 H 12 O 6 as glycogen and use the amino acids to make proteins.
  • 72. Nucleic Acids:
    • Nucleotides diffuse into epithelial cells , and then diffuse into capillary bed/network  enter the bloodstream  liver via hepatic portal vein  hepatic vein  heart  body cells.
  • 73. H 2 O:
    • Enters epithelial cells by osmosis and into the capillary bed/network  enters bloodstream.