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Digestive System

Digestive System. Digestive System - basic plan. Mouth (toothed jaws, oral valves) Oral cavity (vomerine, palatine teeth, tongue w/ teeth) Pharynx (pharyngeal tooth pads, gill arches/rakers) Esophagus (gullet) Stomach. Digestive System - basic plan. Pylorus (pyloric valve, pyloric caeca)

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Digestive System

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  1. Digestive System

  2. Digestive System - basic plan • Mouth (toothed jaws, oral valves) • Oral cavity (vomerine, palatine teeth, tongue w/ teeth) • Pharynx (pharyngeal tooth pads, gill arches/rakers) • Esophagus (gullet) • Stomach

  3. Digestive System - basic plan • Pylorus (pyloric valve, pyloric caeca) • Small intestine (ducts bring in bile, pancreatic secretions) • Large intestine/cloaca • Anus

  4. Variation based on diet, lifestyle

  5. Mouth & Oral Cavity

  6. Teeth in Jaws • Food generally swallowed whole • Teeth used for capture, not chewing

  7. Pharynx - gill rakers

  8. Gill rakers • Gill rakers on anterior side of each gill arch - prevent escape of prey • Gill filaments on posterior side of each gill arch

  9. Size and shape of rakers depend on types of foods eaten

  10. Short, blunt gill rakers • Large prey

  11. Long, fine gill rakers • Particle or suspension feeder

  12. Developmental changes • Gill rakers can change in form as fish develops

  13. Paddlefish - suspension feeder • Long, fine gill rakers to strain plankton from water column

  14. Zooplankton’s view!

  15. Pharyngeal teeth

  16. Pharyngeal Teeth • Variety of teeth in the same general region • Derived from gill arches

  17. Feeding

  18. Pharyngeal teeth • Aid oral teeth in holding “prey”, directing them into esophagus • Modified for crushing, grinding, shearing of foods

  19. Pharyngeal Teeth • Present in many herbivores that eat plants, algae, and/or phytoplankton • E.g., Grass carp

  20. Esophagus & stomach • Structure varies with diet • Simple tube to blind-sac, elastic pouch

  21. Pylorus • Pyloric valve controls release of stomach contents • Ray-finned fishes peculiar among vertebrates • Possess numerous pyloric caeca - digestive/secretory glands Pyloric caeca

  22. Intestines

  23. Carnivore intestines • Intestine usually very short in carnivores • Animal foods digested, absorbed easily

  24. Herbivore intestines • Intestine usually very long in herbivores, detritivores • Plant foods digested, absorbed slowly

  25. Chondrichthyes

  26. Shark digestive system

  27. Spiral valve in sharks Increases food passage time through intestine - improves absorption

  28. Typhlosole in lampreys • Flap of tissue extending • into lumen of intestine • increases surface area • for absorption • Disclaimer - this is a • picture of an earthworm, • not a lamprey

  29. Circulatory System • Fish have a single-loop circulatory system

  30. Typical pathway Heart to gills to body, back to heart

  31. Major vessels run along (ventral to) vertebral column Branches to organs, muscles (segmental)

  32. Heart • Fish have a 2-chambered heart

  33. Lungfish Circulatory System • Lungfish have added features

  34. Lungfish Circulatory System

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