ZooLec

• Digestive system


  Organ system responsible for breaking down food and liquids, absorbing its nutrients, and expelling any remaining waste
• Main regions of the digestive system

  • Digestive tract
  • Accessory digestive glands
• Digestive tract


  Tubular passageway that extends from the mouth to the anus or cloacal opening
• Components of the digestive tract

  • Buccal cavity
  • Pharynx
  • Alimentary canal
• Buccal cavity


  Also known as oral cavity or mouth, entry point of food into the digestive system
• Main function of the Buccal cavity

  • Mastication or chewing
  • Chemical digestion
• Palate


  Roof of the mouth, formed from the fusion of ventral skull bones overlying the mouth
• Palate


  • Prevents food and liquid from entering the nasal cavity
  • Enables suckling in mammal infants
• Teeth


  Hard, bony, enamel-coated structures that help catch, hold, and break down prey/food
• Hard tissues of the teeth

  • Enamel
  • Dentin
  • Cementum

  
• Tongue


  Set of muscles that facilitates movement of food during mastication and assists swallowing
• Tongue


  • Holds the taste buds, vomeronasal organ (Jacobson's organ), and filiform papillae
  • Helps in lingual feeding, chewing, swallowing, and taste
• Pharynx


  Passageway of air via the trachea and delivers food to the stomach through the esophagus
• Pharynx

  • Glottis
  • Epiglottis
• Alimentary canal


  Where further breakdown of bolus, absorption of its available nutrients, and elimination of indigestible remnants occur
• Esophagus


  Slender muscular tube that connects the pharynx with the stomach and easily becomes distended to accommodate a large bolus
• Esophagus


  • Seldom produces enzymes that contribute to chemical digestion
  • Smooth muscles undergo peristalsis to push food toward the stomach

  
• Stomach


  Expanded region of the alimentary canal that receives the bolus delivered by the esophagus

  
• Stomach


  • Churns and mixes food mechanically and adds gastric juice
  • Serves as temporary storage compartment
  • Some absorption of water, salts, and vitamins
• Small intestine


  Long tube-like organ with a highly folded surface containing finger-like projections called the villi

  
• Small intestine


  • Secretes enzymes for the digestion of proteins, carbohydrates, and lipids
  • Selectively absorbs the final products of digestion
  • Moves food along the digestive tract via peristalsis

  
• Sections of the small intestine

  • Duodenum
  • Jejunum
  • Ileum

  
• Large intestine


  Tube that connects the small intestine to the cloaca or anus, named for its large diameter

  
• Large intestine


  • Reabsorbs water and mineral salts from undigested material
  • Processes and stores waste material
• Structures at the end of the large intestine

  • Cloaca
  • Rectum

  
• Accessory digestive glands

  • Salivary glands
  • Liver
  • Pancreas
• Salivary glands


  Secrete a watery substance that moistens and lubricates the food, helps maintain healthy oral membranes, neutralizes toxins carried by prey, and initiates chemical stages of digestion
• Saliva


  • Contains immunoglobulins and lysozymes, amylase, and trypsin
• Liver


  Second largest organ in the body, detoxifies and removes toxic substances from the blood, stores and metabolizes carbohydrates, proteins, and fats, manufactures bile
• Pancreas


  Releases pancreatic juice that contains proteolytic enzymes and bicarbonate, secretes amylases and lipases
• Unique features of the buccal cavity in fishes

  • Mouth and lips
  • Teeth
  • Tongue
  • Gizzard
  • Stomach
  • Pyloric caeca
• Mouth and lips of fishes


  • Vary based on feeding habits like surface feeders, filter feeders, and predatory fish
• Teeth of fishes


  • Vary depending on diet and feeding habit, dermal origin, scattered on roof of mouth and attached to cartilaginous jaw, pointed towards pharynx
• Tongue of fishes


  Primary tongues are thick and immovable pads in the lower jaw, used as a sensory organ rather than for tasting
• Gizzard in fishes

  Modification of the first part of the stomach, functions to grind coarse food intake mechanically
• Stomach of fishes


  Serves as a pathway and storage for food, highly acidic and secretes hydrochloric acid
• Pyloric caeca


  Thin tubes that connect to the stomach, store and secrete digestive enzymes, neutralize acidity
• Goblet cells in fishes


  Unicellular glands that produce mucus to help push food down the digestive tract
• Stomach glands in fishes


  Produce enzymes like trypsin to chemically break down food
• Liver in fishes


  Produces bile to break down fats