Intro To Vet A & P - Exam 3

• Monogastric


  The digestive system of the carnivore is described as monogastric. The tract is relatively short, because meat is easy to digest and the stomach is simple.
• Carnivore teeth


  • Sharp, pointed and powerful
  • Jaw has a scissor-like action to cut and tear off the bones of prey
• The majority of the tract is a long tube of varying diameter. Each part has a similar structure but shows functional adaptations.
• Food passage through the digestive tract

  1. Passes down the tract

  2. Mixed with digestive juices by coordinated muscular movements (peristalsis and rhythmic segmentation)
• Digestion


  Occurs by the action of enzymes, each of which is specific to a particular food type
• Digestive juices containing enzymes are secreted by

  • Intrinsic exocrine glands in the stomach and small intestine
  • Extrinsic glands such as the pancreas and gall bladder
• Digestion results in


  Production of soluble molecules that can pass through the epithelium of the small intestine into the blood capillaries (amino acids and monosaccharides) or lacteals (fatty acids and glycerol)
• The products of digestion are carried around the body where they are metabolised and used by the tissues.
• Any unwanted or indigestible food remains are excreted in the faeces.
• Ingestion


  The process of taking food into the body; this takes place in the mouth.
• Digestion


  The process of breaking down the food into small chemical units; this occurs in the stomach and small intestine.
• Absorption


  The process whereby the chemical units pass into the blood and are carried to the liver; this occurs in the small intestine.
• Metabolism


  The process in which the chemical units are converted into energy for use by all the organs of the body; this takes place mainly in the liver.
• Excretion


  The removal of any remaining indigestible material.
• Parts of the digestive system

  • Oral cavity (mouth, lips, tongue, teeth)
  • Pharynx
  • Oesophagus
  • Stomach
  • Small intestine (duodenum, jejunum, ileum)
  • Large intestine (caecum, colon, rectum, anus)
• Accessory glands


  • Salivary glands
  • Pancreas
  • Gall bladder
  • Liver
• Functions of the oral cavity

  • Pick up food (prehension)
  • Break up food into small boluses to aid swallowing (mastication or chewing)
  • Lubricate food with mucus and saliva to aid swallowing
  • In omnivores and herbivores, begin digestion of carbohydrates with salivary enzymes (does not occur in carnivores)
• Bones forming the oral cavity

  • Incisive bone and maxilla (upper jaw)
  • Palatine bone (hard palate)
  • Mandible (lower jaw)

  
• Temporomandibular joint


  Allows a scissor-like action in carnivores to shear flesh off the bones of their prey
• Tongue


  • Aids ingestion of food
  • Carries taste receptors (taste buds)
  • Helps form food bolus for swallowing
  • Grooms fur
  • Assists thermoregulation
  • Produces vocalisation
• Tongue structure


  • Made of striated muscle fibres running in all directions, enabling delicate movements
• Brachyodont teeth


  Fairly low in profile and cease growing once they reach their final size (in contrast to hypsodontic teeth of herbivores)

  
• Tooth structure


  • Pulp cavity containing blood capillaries and nerves
  • Enamel covering the upper surface
  • Dentine forming the main part of the tooth
  • Cement holding the tooth firmly in the gum

  
• Tooth types


  • Incisors
  • Canines
  • Premolars
  • Molars
  • Carnassial

  
• Deciduous dentition


  Milk or temporary teeth present at birth and erupting as the animal grows, smaller and whiter than permanent teeth

  
• Permanent dentition


  Adult teeth, larger and more creamy in colour than milk teeth, lasting a lifetime
• Eruption times vary with species, tooth type, and animal species
• Dog dental formula


  • Permanent: (I3/3, C1/1, PM4/4, M2/3) x 2 = 42 teeth
  • Deciduous: (I3/3, C1/1, PM3/3) x 2 = 28 teeth
• Cat dental formula


  • Permanent: (I3/3, C1/1, PM3/2, M1/1) x 2 = 30 teeth
  • Deciduous: (I3/3, C1/1, PM3/2) x 2 = 26 teeth
• Dog dental formula


  • Permanent: (13/3, Cl/1, PM4/4, M2/3) x 2 = 42 teeth
  • Deciduous: (13/3,Cl/1, PM3/3) x 2 = 28 teeth
• Cat dental formula


  • Permanent: (13/3, Cl/1, PM3/2,Ml/1) x 2 = 30 teeth
  • Deciduous: (13/3, Cl/1, PM3/2) x 2 = 26 teeth
• Dental formulae


  Each species has a characteristic dental formula and this enables the veterinary surgeon to monitor the numbers of teeth

  
• Tooth types and functions

  • Incisors: Fine nibbling and cutting meat; often used for delicate grooming
  • Canines: Holding prey firmly in the mouth
  • Premolars: Shearing flesh off the bone using a scissor-like action; flattened surface helps to grind up the flesh to facilitate swallowing and digestion
  • Molars: Shearing and grinding meat
  • Carnassials: Very powerful teeth sited close to the angle of the lips; only found in carnivores
• Eruption times


  • Dog: Deciduous dentition starts at 2 weeks and is complete by 4 weeks; Permanent dentition from 3.5-4 months to 12 weeks
  • Cat: Deciduous dentition starts at 2 weeks and is complete by 4 weeks; Permanent dentition variable, full dentition present by 6 months
• Fig. 9.5. Skull of an adult dog showing the permanent dentition
• Swallowing (deglutition)


  1. Food is rolled into a bolus by the tongue and cheeks and passed to the back of the mouth

  2. Pharyngeal muscles contract and force the bolus towards the oesophagus

  3. Epiglottis closes to prevent food and air entering the larynx

  4. Peristalsis pushes the food down the oesophagus

  5. Epiglottis falls open again and air is able to pass into the trachea
• Oesophagus


  Simple tube that carries food from the pharynx to the stomach
• Salivary glands


  • Paired glands around the oral cavity that secrete saliva
  • Saliva contains 99% water and 1% mucus; no enzymes in dog and cat saliva
  • Positions: zygomatic, sublingual, mandibular, parotid
• Pharynx


  Muscular tube lined with mucous membrane, connecting the back of the nasal and oral cavities with the oesophagus and the larynx and trachea
• Eustachian tube


  Connects the pharynx to the middle ear, enabling air pressure equalisation on either side of the tympanic membrane