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Digestive System

Digestive System. Overall Function Ingestion Digestion (physical & chemical) Absorption Waste elimination. Development. Coelom forms from splitting of lateral plate mesoderm (hypomere) This is the pleuroperitoneal cavity through reptiles Parietal peritoneum Visceral peritoneum

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Digestive System

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  1. Digestive System • Overall Function • Ingestion • Digestion (physical & chemical) • Absorption • Waste elimination

  2. Development • Coelom forms from splitting of lateral plate mesoderm (hypomere) • This is the pleuroperitoneal cavity through reptiles • Parietal peritoneum • Visceral peritoneum • Dorsal & Ventral mesentery are folds of peritoneum

  3. Endoderm • Foregut • Midgut • Hindgut

  4. General Morphology • Typical gut wall has MUCOSA, SUBMUCOSA, MUSCULARIS, SEROSA

  5. Gut motility • Peristalsis • Segmentation

  6. Oral cavity/Oropharyngeal cavity • Tongue – can extend from mouth beginning with amphibians • Anchored by hyoid • Helps to capture food, chew, swallow, taste food

  7. Glands • Venom • Saliva • Including several enzymes • Anticoagulant in lampreys • Nutrients in catfish • Mucus

  8. Snake venoms

  9. Teeth • Dermal armor, dermal plates • Placoid scales • Homology to teeth

  10. Teeth • Dentin forms the majority of tooth and is a bone-like material made by odontoblasts

  11. Teeth • Enamel is the hardest substance in the body due to mineral content and is made by ameloblasts

  12. Teeth • The pulp cavity of the tooth contains the blood vessels and nerves • The cementum covers the root of tooth and is made of acellular bone

  13. Tooth attachment • Acrodont – peak of jaws, teleosts • Pleurodont – inner surface of jaws, amphibians, lizards • Thecodont – sockets, crocodiles, extinct birds and mammals

  14. Sets of teeth • Polyphydont – many sets, typical of most vertebrates • Diphydont – two sets, most mammals • Monophydont – one set, platypus

  15. Feeding Teeth New teeth forming

  16. Shape of teeth • Homodont – fish, amphibians, most reptiles, some marine mammals

  17. Shapes of teeth • Heterodont – later reptiles, most mammals • Incisors - cutting teeth, chisel shaped • Canine teeth – pointed for piercing & tearing • Premolars – grinding teeth with 1-2 roots • Molars – grinding teeth with 3 roots

  18. Dental formulas • Human: 2-1-2-3/2-1-2-3 = 32 • Cat: 3-1-3-1/3-1-2-1 = 30 • Cow: 0-0-3-3/3-1-3-3 = 32

  19. Key Points • What do you find unusual about the cow’s dental formula? • What does this tell you about their eating habits? • Can you think of another animal that would have the same unusual feature?

  20. Herbivore

  21. Pharynx • Fish – respiratory (gill) in function • Tetrapods – throat, swallowing, location of tonsils in mammals

  22. Pharynx in Tetrapods • Common opening to airways via glottis • Opening to middle ear via auditory tubes • Opening to esophagus

  23. Esophagus • Can close in fish so stomach doesn’t become filled with respiratory water • Birds may have CROP – sometimes has digestive enzymes & allows hoarding of food • Pigeon milk is an esophageal secretion in doves for nestlings

  24. Stomach • Gastr- • Anatomy –one or more chambers • Pylorus, pyloric sphincter • Greater & Lesser curvature • Greater omentum, mammals only

  25. Stomach • Proventriculus – Contains digestive enzymes in birds (& crocodiles) • Gizzard –grinding mill in bird

  26. Ruminant Stomachs • Rumen – cellulase & mucus release • Reticulum – bolus formation for regurgitation • Omasum – holding tank • Abomasum – glandular portion

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