Digestive System

• Tunicates/cephalochordates

  • Suspension/filter feed
  • no stomach
  • ciliated pharyngeal arches
• lamprey/hagfish

  • Horny keratinous cones - no stomach
  • mucus secreting glands
  • suspension/filter feed
  • ciliated pharyngeal arches
• Chondrichthyans

  • ram-feeding
  • can also use some biting and suction
  • tooth whorl
• Actinopterygii

  • Suction-feeding through pharyngeal expansion
  • Gill rakers for feeding
  • ram feeds with suction and biting
• Amphibians

  • A few aquatic salamanders and tadpoles use suction feeding
  • Rotational feeding in some salamanders
  • Protrusible tongue in frogs and some salamanders
• Reptiles

  • Compensatory suction-feeding in aquatic turtles
  • Rotational feeding in crocs
  • Cranial kinesis in squamates and birds
  • Protrusible tongue
  • Birds have a crop and gizzard
  • Venom in some squamates
• Mammals

  • Typically diphyodont and homo or heterodont depending on feeding preference (carnivore, herbivore, omnivore)
  • Extensively developed oral glands
  • Ruminant animals have chambers
• Chondricthyans and actinopterygiians both have no oral glands and use a combo of ram, suction and biting (especially ram)
• Ingestion - intake of food
• Mastication - processing of food
• Deglutition - swallowing
• Duverney’s gland -> venom
• Acrodont - replacement teeth already present
• Pleurodont - replacement teeth in jaw
• Theodont - replacement teeth in jaw but limited
• Homodont - similar tooth shapes
• Heterodont - different tooth shapes
• Polyphyodont - multiple replacements
• Diphyodont - 2 set
• Monophyodont - 1 set
• Aquatic turtles use compensatory suction feeding, where a hyoid depression creates suction, but food is not sucked into the mouth. It's kept in place for ram feeding
• Most tetrapods capture food using their jaw or tongue
• tetrapod feeding cycle

  1. slow opening of mouth
  2. fast opening
  3. fast closing
  4. slow closing - power stroke
• In squamates, the pre-maxilla can detach from the brain case to increase gape
• Initial protein digestion occurs in the stomach, the intestine is the main site of digestion and absorption