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Digestive System II

Digestive System II. SBI3U Ms. De Sousa. How Animals Obtain their food. Autotrophs : Take energy from the environment in the form of sunlight or inorganic chemicals Use the energy to create energy-rich molecules. Examples : plants and algae. How Animals Obtain their Food.

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Digestive System II

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  1. Digestive System II SBI3U Ms. De Sousa

  2. How AnimalsObtaintheirfood Autotrophs: • Take energy from the environment in the form of sunlight or inorganicchemicals • Use the energy to create energy-rich molecules. • Examples: plants and algae

  3. How AnimalsObtaintheir Food Heterotrophs: • Take in autotrophsas food. • Depend on autotrophs for the energy and raw materials they need • Heterotrophs obtain energy by breaking down organic molecules obtained from the autotrophs • Examples: all animals, mostfungi, bacteria and protozoa.

  4. Autotrophs and Heterotrophs

  5. Animals (i.e. heterotophs) • Have adaptedmechanisms to search, obtain and take in theirfood. • Animalsobtainfoodfromeither of the following 4 mechanisms.

  6. FeedingMechanisms 1) FilterFeeding: • Use a filter basket to obtainorganismssuspended in the water. • Siphon water intoitsmouth and filtersit to obtainitsfood. Examples: Tube worms, clams, whales

  7. FilterFeeding in Sponges Video

  8. FeedingMechanisms 2) SubstrateFeeding: • Live within or on the food source and eattheirwaythroughit. • Examples : Earthworms, caterpillars

  9. FeedingMechanisms 4) Bulk Feeders: • Most vertebrates (includinghumans). • Ingest large pieces of food or swallowitwhole. • Differentanimalsmay use tentacles, pincers and claws to eat.

  10. FeedingMechanisms 3) Fluid Feeders: • Suck or lickfluidsform plants or animals. • Theirmouth parts are adapted to piercethrough skin or leaf tissue. • Examples: spidders, bees, butterflies.

  11. Digestive Tract • In order for the cells to obtainnutrients, the digestive system needs to break them down intosmall, soluble units. • The smallunits of nutrientsdiffuse intocell membranes and into the circulatory system.

  12. Alimentary Canal • Most animals have a digestive tract alsoknown as « Alimentary Canal » • Alimentary Canal: tube wherefood in processed, beginningat the mouth and endingat the anus. • There are variousorgansalong the alimentary canal thatprocess the food.

  13. Alimentary Canal Pouchlike structure thatsoftens and stores food Example: Earthworm Churns and grinds the food

  14. All organs in the digestive system play a vital role in the process of digestion. Eachorganisresponsible for eitherbreaking down the food, abosrbingit or deliveringit to other areas.

  15. Similarities and Differences • The function of the alimentary canal is the same for all animals. • The lengthdiffersaccording to feeding habits. • Herbivores and Omnivores have longer digestive tracts thanCarnivores.

  16. Stages of Digestion • No matter the feedingmechanisms all animalsundergoe the same 4 stages of digestion. a) Ingestion b) Digestion c) Absorption d) Elimination

  17. Stages of Digestion • Ingestion:Taking in the food • Digestion: Breakdown of foodintosmallmolecules • Absorption: diffusion of smallmoleculesinto the circulatory system • Elimination: removal of undigestedsolidwastefrom the body.

  18. Main Types of Digestion: Mechanical: physical breakdown of macronutrients (i.e. chewing, churning) Chemical: chemical breakdown of nutrientsintosmallermolecules by hydrolysisand enzymatic action.

  19. 10.2 The Human Digestive System The digestive tract has numerousorganswithspecificfunctions. Eachorganhelpsto breakdown food.

  20. DIAGRAM OF DIGESTIVE SYSTEM: Mouth Esophagus Liver Stomach Pancreas Gallbladder Small Intestine Large Intestine Rectum Appendix Anus

  21. STEP 1: INGESTION Mouth Mechanical digestion: Teethbreakdown the foodintosmallpieces Chemical digestion: Amylase (enzyme) breaks down the bonds in carbohydrates.

  22. Salivaissecretedfrom 3 salivaryglands. • The secretion of saliva istriggeredbeforeyou have food in yourmouth.

  23. Role of Saliva (Chemical Digestion) • Amylase (enzyme) breaks down carbohydratesintosimplersugars. • Dissolves water soluble foodparticles • Stimulates taste buds. • Lubricates the foodsoitcanbeswallowed.

  24. When the mouth has created a bolus of food, the tongue pushes it back into the back of the throat. • Epiglottis – flap covers trachea so food doesn’t get in • Food stretches walls of esophagus and moves downward through waves of contractions called peristalsis

  25. Esophagus • Glands in the liningproducemucuswhichkeeps the tube moist and facilitatesmovement of food. • The muscles in the esophaguscontractinvoluntarily to push the bolus of foodinto the stomach. Video

  26. Esophagus • When the bolus of food has reached the bottom of the esophagus the EsophagealSphincter opens. • Whileswallowing, the muscles relax, opening the sphincter and allowing the food to enter the stomach.

  27. The esophageal sphincter usuallyremainsclosed to preventacidicjuicesfromflowing up into the esophagus. Acid Reflux Video

  28. STEP 2: DIGESTION Stomach • Muscular, J-shapedorgan • Leftside of the abdominal cavitybelow the diaphragm • Performsbothchemical and mechanical digestion

  29. Stomach • The walls of the stomach are foldedsothatitcanexpandafter a meal. • The glands on the stomachwall release « gastricjuice » whichconsist of HCl, salts, enzymes, water and mucus. (chemical digestion) • The walliscovered in a mucus coatwhichprotectsitfrom the acidreleasedfrom the gastricjuices.

  30. Stomach Pepsinis the enzyme released. Pepsinremains inactive (pepsinogen) untilHClissecretedform the glands. Once activated, pepsinhydrolyzesproteins.

  31. Stomach • The HCl breaks down food and destroys foreignbacteria in the food. • Stomachcontracts and relaxes to churn the food. • The churninghelpsto break up the foodand mix the gastricjuices. • Food + Gastricjuices = Chyme

  32. Pyloric Sphincter The Pyloric Sphincter opens to move the chyme into the small intestine.

  33. STEP 2: DIGESTION Cont’d Small Intestine • Furtherbreaks down and abosrbsnutrients. • Composed of three main components: 1) Duodenum 2) Jejunum 3) Illeum

  34. Duoedenum • Receivessecretions(enzymes) fromthe gallbladder and pancreasto further breakdown nutrients. • The intestinal glands also release trypsin and chymotrypsin (enzymes) to breakdown carbohydrates and proteins. • Breaks down proteins, fats and carbohydrates.

  35. Jejunum • 2.5 m long. • Contains more foldsthan the duodenum. • Breaksdown the remainingproteins and carbohydratessothatitcanbeabsorbed.

  36. Villi and Microvilli • Small intestine iscoveredby tinyfinger-likeprojections called« Villi » • The villiincreases the surface area for absorption of nutrientsinto the bloodstream. • There is a capillary network within the villi. The nutrients diffuse from the small intestine into the villiwherebyitthen diffuses into the capillary network.

  37. Illeum • 3 m long. • Has fewervillithan the dueodenum and jejunum. • Absorbsnutrientsthrough the villiand pushesundigestedmaterialinto the large intestine.

  38. STEP 3: ABSORPTION Small Intestine and Large intestine The villi and microvilliincrease surface area for absorption. The nutrients diffuse into the capillarieswithin the villi.

  39. STEP 3: ABSORPTION Small Intestine and Large intestine • Large intestine (colon) is 1.5 m in length • Reasborbs90% of water and electrolytesback into the blood. • Bacterialive hereproducingvitamin K /B and break down undigestedmatter. • Anyundigestedmaterialthatremainsiscalledfeces. • Fecalmatterisstoredhere for eliminationthrough the rectum.

  40. STEP 4: ELIMINATION Rectum Main component of feces: • Cellulose- makes up plant cell walls, cannot be digested by humans • Living and dead bacteria • Water • Toxic wastes are removed • People who don’t eat enough cellulose (plant material and fibre) have fewer bowel movements and are at risk of colon cancer.

  41. AccessoryOrgans

  42. Pancreas • Secretes about 1 L of pancreaticfluidinto the duoedenumeachday. • PancreaticFluid: 1) Lipase (enzyme) – chemically digest lipids 2) Bicarbonate– alterspH of chyme sothatenzymescanbeactivated. (pH 1 to pH 8)

  43. Liver • Largestinternalorganin the human body. • Releases bile (greenish-yellowfluid made up of bile pigments and salts) • Bile is sent to the gallbladderwhereitistemporarilystored.

  44. Bile • Fats are insoluble in water and remainsuspended in the chyme. • The bile salts break up the fat dropletssotheycan disperse through the chyme. • The enzymes break the dropletsapart. Video http://www.youtube.com/watch?v=Z7xKYNz9AS0

  45. Enzymes – proteinsthat speed up chemicalreactions Digestive Enzymes Induced Fit Model The substrate and enzyme have complementaryshapes. Thusmakingthem fit perfectlyinto one another. Therefore, the enzyme ishighlyspecific to itssubstrate.

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