Module 6: Digestive System

• Ingestion


  The process of taking food into the body
• Digestion


  Breaking down food into small chemical units
• Absorption


  Nutrients go into the bloodstream and are carried into the liver
• Metabolism


  Chemical units are converted into energy
• Excretion


  Removal of any remaining indigestible material out of the body
• Digestive system of the dog

  • Monogastric, digestive tract is short, stomach is simple
• Parts of the alimentary canal

  • Oral cavity or mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
• Oral vestibule


  Space between the lips and the teeth
• Proper oral cavity


  Bounded rostrally by the lips, laterally by the cheeks, dorsally by the hard palate, and ventrally by the tongue
• Lips


  • Form the rostral and most of the lateral external boundaries of the vestibule
• Philtrum


  A deep, straight, narrow cleft that marks the union of the two halves of the upper lip, anteriorly
• Cheeks


  Form the caudal portion of the lateral walls of the vestibular cavity
• Hard palate


  Palatine, maxilla, and the incisive bones (premaxilla)
• Soft palate


  Resection or amputation is the surgical process of removing a portion to enable the easy flow of air
• Teeth


  • Brachydont in dogs and cats, fairly low in profile
• Tooth structure


  • Root
  • Crown
  • Neck
• Enamel


  Hardest part of the tooth and the hardest part of the body, produced by the ameloblast, shiny white outer covering
• Dentine


  The bulk of the tooth contains the dental cavity, forms the main part of the tooth
• Pulp cavity


  Mass of connective tissues, blood vessels and nerves, produced by odontoblast, contains blood capillaries and nerve fibres
• Cement/Cementum


  A thin bone-like layer, holds the tooth with the gum, holds the tooth firmly in the gum
• Dentition


  • Deciduous dentition (milk or temporary teeth)
  • Permanent dentition (adult teeth)
• Teeth groupings


  • Incisors
  • Canines
  • Premolars
  • Molars
  • Carnassial
• Dogs and cats have two sets of teeth in their lifetime
• Tooth surfaces


  • Vestibular surface
  • Lingual surface
  • Contact surface
  • Mesial surface
  • Distal surface
  • Occlusal surface
• Tongue


  • Lies on the floor of the oral cavity, free apex, meaty body and caudal root, striated muscle fibers running in all portions
• Functions of the tongue

  • To aid the ingestion of food
  • To carry the receptors for the sensation of taste
  • To help in the formation of a food bolus ready for swallowing
  • To groom the fur
  • To assist thermoregulation
  • To produce vocalization
• Mechanical papillae


  • Filiform papillae
  • Conical papillae
  • Marginal papillae
• Gustatory papillae


  • Fungiform papillae
  • Foliate papillae
  • Vallate papillae
• Pharynx


  Also known as the throat, muscular tube in the neck that connects the respiratory and digestive systems, has three parts: nasopharynx, oropharynx, and hypopharynx/laryngopharynx
• Pharyngeal openings


  • Pharyngeal opening (isthmus of fauces)
  • Caudal nares (choana)
  • Pharyngeal openings of the auditory tubes
  • Laryngeal opening (aditus laryngeus)
  • Esophageal opening
• Esophagus


  • First part of the alimentary canal, divided into three regions: cervical, thoracic, abdominal (shortest), muscles: cricopharyngeus muscle and cardiac muscle
• Esophagogram


  Application of barium, then a series of radiographs is conducted to assess the gastrointestinal track passageway when there is obstruction of foreign things in the esophagus that results in food cannot pass through
• Stomach


  • Simple in cats and dogs, monogastric, has an inlet (cardia) and an outlet (pylorus)
• Functions of the stomach

  • To act as a reservoir of food
  • To break up the food and mix it with gastric juices
  • To begin the process of protein digestion
• Stomach surfaces


  • Parietal surface
  • Visceral surface
• Parts of the stomach

  • Fundus
  • Cardia
  • Pylorus
  • Greater curvature
  • Lesser curvature
  • Cardiac orifice
  • Cardiac sphincter
  • Body
  • Pyloric antrum
  • Pyloric canal
• Greater curvature


  Convex and extends from the cardia to the pylorus, approximately 30 cm long in a moderately filled stomach
• Lesser curvature


  Short concave portion of the stomach that extends from the cardiac to the pylorus
• Cardia or cardiac ostium


  First part of the stomach connected to the esophagus, houses the gastroesophageal sphincter
• Cardiac Orifice


  Opening where the esophagus connects with the stomach