Digestive-1

• 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
• 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
• 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.
• 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
• The basic plan of the digestive system in all vertebrates are generally the same. However, some components or structures may vary due to their diet
• BUCCAL CAVITY

  3 Main components: Palate, teeth, and tongue
• ALIMENTARY CANAL

  4 Main components: Esophagus, stomach, small intestine, and large intestine.
• What happens inside the buccal cavity?

  • Mastication or chewing
  • Chemical digestion
• The chewing and wetting action prepare the food into

  the bolus for swallowing.
• Enamel

  • Hardest substance in the body and forms the surface of the tooth crown

  Dentin

  • Resembles bone in chemical composition, but is harder. and forms the walls of the pulp cavity.

  Cementum

  • Has cellular and acellular regions like the bone. It rests upon the dentin and grows in layers on the surface of the roots.
• Crown


  Part of the tooth projecting above the gums
• Root 


  Part of the tooth that is below the gums and is anchored to the jawbone.
• PULP


  Fills the pulp cavity and root canal to support blood vessels and nerves that enter through the opening found at the tip of the root.
• OCCLUSAL SURFACE


  Part of the crown that makes contact with opposing teeth.
• CUSPS


  Tiny, raised peaks at the occlusal surface.
• GLOTTIS


  Slit opening into the larynx, which leads to the

  opening into the esophagus.
• EPIGLOTTIS


  Cartilaginous flap that

  prevents food from entering the larynx
• Function of the esophagus depends

  on the epithelial lining and diet


  In some vertebrates, the ciliated epithelial lining of

  the esophagus controls the flow of lubricating mucus

  around the food and help gather small crumbs from

  the meal and move these along to the stomach