Comparison: The Digestive System

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DesLee26
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311333
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Comparison: The Digestive System
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2015-11-11 16:45:24
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Vertebrates
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  1. Vertebrate teeth
    Unique among vertebrates, usually capped with enamel

    Lacking teeth: turtle and birds
  2. General characteristics of teeth in lower vertebrates
    Homodont: teeth similar in appearance throughout mouth

    Polyphyodont dentition: teeth are continuously replaced; ensures rejuvenation of teeth if worn/ broken
  3. General Characteristics of tetrapods
    Heterodont- teeth differ in appearance throughout mouth

    Polyphyodont- repitles

    • diphyodont: two sets of teeth (mammalian)
    • --> 1st set: deciduous dentition- milk/early teeth
    • --> 2nd set= permanent dentition- adult/ mature teeth (includes molars)
  4. Vertebrate teeth attachment
    • acrodont
    • pleurodont
    • thecodont
  5. acrodont
    teeth attached in shallow sockets within the top surface of the jaw bone (weakest)

    --> not very strong

    --> allows for rapid replacement
  6. Pleurodont
    teeth attached on the inner side and upper side of the jawbone that increases jawbone attachment area

    • --> still conducive to polyphodont, but not as much
    • --> stronger than acrodont, supports rapid replacement
  7. Thecodont
    • Teeth attached by roots that are firmly fixed into sockets within the jawbone
    • - strongest vertebrate tooth attachment
    • - Largest surface area of tooth to jawbone
  8. Specialized teeth of lower vertebrates: teleost fish
    most teleost fish--> teeth form abrasive surfaces used to scrape algae from rocks

    --> acrodont tooth attachment
  9. Specialized teeth of lower vertebrates: sharks
    teeth have sharp, knifelike edges along sides to pierce the skin; acrodont tooth attachment
  10. Specialized teeth of lower vertebrates: salamanders
    • Differences between larval and metamorphosed adults
    • - larval: pointed cone-shaped
    • - adults: specialized teeth are bicuspid (having 2 cusps) and crown sits upon a basal pedicel, attached by collagenous fibers

    --> when tooth replaced, crown is lost and pedicel quickly resorbed for rapid tooth replacement (acrodont tooth attachment)
  11. Reptilian teeth
    display acrodont (snakes), thecodont (alligators), and pleurodont (lizards) tooth attachment
  12. Carnivorous reptiles
    • teeth have sharply pointed cusps that penetrate skin and provide a firm hold on prey
    • --> reverse curved teeth in front of mouth
    • --> tip of tooth inclined forward from the rest of the tooth: better for grasping prey/ preventing escape- maxillary teeth
    • --> open groves down which oral secretions flow during feeding
    • --> venomous snakes: fangs- ends fuse to form a channel for venom from venom duct
    • --> polyphyodont (regular replacement)
  13. Mammalian teeth- attachment
    thecodont
  14. Mammalian teeth- types of teeth
    four- incisors, canines, premolars, molars
  15. Mammalian teeth- Crown variations
    brachydont-low crowns (humans, pigs)

    hypsodont- high crowns (horses)
  16. Mammalian teeth- Cusp variations
    • -rounded peaks [omnivores])
    • -lophodont (cusps drawn out into predominately straight edges [horses, rhinos])
    • - selenodont (crescent-shaped cusps (camels, deer))
  17. Specialized mammalian teeth
    sectorial teeth

    carnassials 

    tusks
  18. sectorial teeth
    modified teeth with ridges on opposing teeth that slice by one another to cut tissue
  19. carnassials
    used to cut sinew and muscle
  20. Tusks
    • modified, elongated teeth
    • --> elephants (incisors), Narqhals (spiraled upper left incisor), walrus (downward upper canines)
  21. Oral glands
    groupings of epithelial cells that line the buccal cavity and secrete mucous and serous fluids
  22. Oral glands- fish
    fish- rarely present due to moistening from watery medium
  23. Oral glands- tetrapods
    prevalent

    • -lack watery medium to moisten food
    • --> salivary glands- most common, form and secrete saliva
    • --> saliva: contains mucous, salts, proteins, and enzymes such as amylase (starch digestion)
  24. Oral glands- amphibians
    Amphibians: mucous glands on tonge and a large intermaxillary gland located within the palate
  25. Oral glands- birds
    • birds: most birds, especially water feeding birds, lack oral glands
    • --> some passerine birds (perching birds with 3 toes and 1 toe back) use mucous oral secretions to aid in nest building
  26. Oral glands- reptiles
    strips of glandular tissue (supralabial and infralabial glands) along upper and lower lips
  27. Types of oral glands in reptiles
    • - lingual and sublingual glands (tongue)
    • - premaxillary and nasal glands (snout)
    • - palatine glands (roof of mouth)
    • - Lacrimal and Hardesian glands
    • - Duvernoy's gland (non-venomous snakes):
    • - Venom gland (Duvernoy's homolog in venomous snakes)
  28. lingual and sublingual, premaxillary and nasal, palatine
    release mucous to lubricate prey during swallowing
  29. Lacrimal and Hardesian glands
    secretions bathe the eye and vomeronasal organ
  30. Duvernoy's gland
    Found along posterior upper lip and releases a serous secretion that may help in digestion
  31. Venom gland
    secretes toxic and digestive chemicals
  32. Oral glands- mammals
    most common oral gland= salivary glands to produce saliva for lubrication and digestion

    Found in three major pairs: mandibular, sublingual, parotid

    Zygomatic gland can be found below zygomatic arch in dogs, cats, and other carnivores
  33. Mandibular
    release secretions into floor of buccal cavity
  34. Sublingual
    release secretions into floor of buccal cavity
  35. parotid
    release secretions into floor of buccal cavity
  36. Liver
    All vertebrates possess a liver that has the same basic microscopic structure
  37. What is the structure of the liver?
    composed of sheets of hepatocytes separated by blood sinuses where courses of venous blood returning from intestines and arterial blood from the hepatic artery are filtered through

    Liver is composed of multiple lobes
  38. Liver- snakes
    Snakes- elongated and narrow within the tubular body cavity
  39. Liver: Protochordates/ Amphioxus
    cecum from gut found near embryonic liver in vertebrate embryos, sometimes called the hepatic cecum

    function: site of enzyme production and food absorption
  40. Gallbladder
    function: bile storage and release during digestion
  41. Gall bladder presence or absence
    Absent in jawless fish, most birds, few mammals

    Present in cartilaginous and bony fish, amphibians, reptiles, few birds, most mammals
  42. Pancreas
    present throughout vertebrates as an exocrine (pancreatic cells-digestive enzymes) and endocrine (pancreatic islets- blood glucose regulation) gland, although distinction may not always be discrete
  43. pancreas- jawless fish
    Jawless fish: exocrine pancreas dispersed throughout submucosa and on the liver; Endocrine pancreas distinct, near bile duct; has a diffuse pancreas
  44. pancreas- sharks
    Sharks: forms discrete gland with associated exocrine and endocrine components
  45. Pancreas- sharks
    have a dorsal and ventral pancreas with two distinct structures
  46. Pancreas: bony fish
    distinct exocrine and endocrine pancreas with clearly delineated pancreatic islets
  47. Pancreas- tetrapods
    exocrine and endocrine pancreas always present as discrete organs near the duodenum

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