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Chapter 41 PowerPoint Presentation

Chapter 41

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Chapter 41

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  1. Chapter 41 Digestion

  2. Digestive Systems • Absorb nutrients necessary to maintain life, eliminate wastes • Ingestion • Digestion • Absorption • Elimination • Digestion—process by which food is chemically and mechanically broken down for use by the body

  3. Digestive Systems • No digestive system • Sponges, tapeworms • Absorb only small molecules • Digestion intracellular

  4. Digestive Systems • Incomplete • Cnidarians, planarians • Single body opening (Gastrovascular cavity) • Limited enzymes • Digestion begins extracellularly • Digestion completed intracellularly • No regions w/ specialized function

  5. Digestive Systems • Complete • Annelids, mollusks, arthropods, vertebrates, etc. (most animals) • Two openings (mouth & anus) • Different regions w/ specialized function • Digestion primarily extracellular

  6. Digestive Systems • Continuous feeders • Filter feeders (clams, mussels, barnacles, etc.) • Must complete digestion quickly • Discontinuous feeders • Most animals • Feed periodically • Need storage area in gut

  7. Complete Digestive System • Functions • Mechanical processing & motility • Secretion of digestive enzymes • Chemical digestion • Absorption • Elimination of wastes • Anatomy determined by lifestyle • Carnivore • Herbivore • Omnivore

  8. Mouth • Initial digestion begins • Mechanical break-down of food • No teeth • Worms, birds—swallow food whole • Grinding done lower in digestive tract • Insects—some chew, some suck • Arachnids—no chewing • Suck existing fluids • Inject digestive fluids into prey

  9. Mouth • Teeth • Vertebrates only • Incisors—shearing • Canines—puncture, tearing • Capture prey • Fighting predators or within species • Premolars—grinding • Molars—crushing

  10. Mouth • Herbivores • Plant material tough • Emphasis on grinding, crushing • Broad, flat premolars & molars • Limited or absent canines

  11. Mouth • Carnivores • Animal material easier to mechanically tear • Emphasis on piercing, cutting • Long, pointed canines • Molars & premolars modified for shearing or piercing

  12. Mouth • Omnivores • Combination teeth • Varies based on amount of each type of food

  13. Mouth • Salivary glands • Secrete via ducts into mouth • Lubricate & moisten food • Salivary amylase • Begins to digest starches • Tongue • Grab food • Manipulate food • Taste

  14. Esophagus • Muscular tube • Lined by stratified squamous epithelium • Moves food from mouth to next step • Peristalsis—rhythmic contractions of gastrointestinal tract

  15. Upper GI • Crop • Insects • Annelids • Most birds • Temporary storage

  16. Upper GI • Proventriculus • Birds, many invertebrates • Secretes digestive enzymes • Gizzard • Birds, many invertebrates, some reptiles • Dinosaurs • Thick, muscular walls • Grinding food • Chitinous plates in some insects & mollusks • Birds swallow “grit” to use for grinding

  17. Upper GI • Stomach (monogastric) • Temporary storage • Mechanical churning • Digestive enzymes • Combined functions of crop, proventriculus, gizzard • Pepsin—breaks down proteins • Hydrochloric acid—slows salivary amylase, activates pepsin

  18. Upper GI • Stomach (ruminant) • Cattle, goats, llamas, camels, deer, sheep, etc. • Four-chambered stomach • Rumen, reticulum, omasum, abomasum • Food swallowed, separated in reticulorumen • Solid (cud) regurgitated from reticulum • Cud chewed for further breakdown, then swallowed • Moved to omasum, water & inorganic minerals absorbed • Moves to abomasum, like monogastric stomach

  19. Lower GI • Small intestine • Short in carnivores • Long in herbivores • Duodenum • Jejunum • Ileum

  20. Lower GI • Secretion of enzymes • Intestinal mucosa • Gall bladder • Pancreas • Absorption • Villi—folds of intestinal lining • Microvilli—folds of intestinal cells

  21. Lower GI • Cecum • Single in mammals • Double in most birds & some reptiles • Large in herbivores • Reduced in carnivores • Remove fluids & salts • In herbivores has large numbers of bacteria to break down plant material

  22. Lower GI • Colon (large intestine) • Most food digested & absorbed by this point • Water & waste • Functions to reabsorb water • Diarrhea—water not absorbed properly • Rectum • Storage of feces ready for elimination • Anus • Muscular sphincter controlling elimination of feces

  23. Other Organs • Liver • Secretes bile (breaks down fats) • Many other important functions • Gall bladder • Stores & concentrates bile • Not present in all animals, even if closely related • Absent horse, deer; present cow, goat, sheep • Absent doves; present hawks & owls • Absent rats; present mice • Pancreas • Many enzymes to break down food • Buffers against HCl from stomach