Digestive Systems

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Digestive Systems
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3 classes of animals based on Diet

• 1. Carnivores eat meat dogs and cats
• 2. Herbivores eat plants - cattle, horses,
  and sheep
• 3. Omnivores both plant and animal eaters
  pig and humans

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3 classes of animals based on digestive systems

• Monogastric 1 stomach cant digest cellulose
  (fiber) pigs and humans
• Ruminant 4 stomachs polygastric digest
  cellulose, produce own B vitamins and proteins
  cows and sheep
• Pseudo-ruminant - have 1 stomach, but have
  enlarged cecum that digests cellulose horses
  and rabbits

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Monogastric
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Mouth

• Prehension gathering food teeth, lips, tongue
• Mastication Chewing break food into smaller
  pieces for swallowing teeth and saliva

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• Esophagus transport tube to stomach muscular
  contractions move food down
• Stomach
• conditions pH of 2, churning and contracting to
  mix and grind food
• ingredients food, HCl, enzymes

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Small Intestine

• major site of nutrient absorption
• Glands gallbladder secretes bile used for lipid
  breakdown Pancreas secretes enzymes for protein
  and carbohydrate breakdown
• Functions villi absorb nutrients that have been
  broken down minerals, vitamins, amino acids,
  Fatty acids, simple sugars

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• Large intestine colon
• accumulates wastes
• absorbs water
• Rectum and Anus

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Ruminant
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• Mouth
• Prehension cow tongue is very long
• Mastication graze rapidly, and dont chew much
  1st time
• Esophagus liquids to the reticulum and solids
  to the rumen
• Rumen very large compartment

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• Regurgitation when rumen full, force contents
  back up to re-chew
• Rumination
• re-mastication of cud or bolus
• Bolus ball of grass
• Adds saliva to food
• Esophagus re-swallow food
• Reticulum honeycomb

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Rumen

• fermentation vat
• 30 gal or more
• contains microbes that break down the cellulose
• pH of 6.5 7 for microbes
• releases methane belch
• creates B vitamins and proteins from amino acids
• also contains papalli that absorb nutrients
  released by microbes

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• Omasum filter for large particles grinds them
  down
• Abomasum like the monogastric stomach acidic
• Small intestine same as monogastric
• Large intestine same as monogastric
• Rectum and anus

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Pseudo-Ruminant
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• Mouth
• a. prehension
• b. mastication
• Esophagus
• Stomach
• a. same as monogastric
• b. too small in horses and inactive doesnt
  break down cellulose
• c. require frequent smaller meals

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• Small intestine absorption of nutrients same
  as monogastric
• Still has not digested the cellulose large
  amount
• Cecum
• enlarged area between small and large intestine
• contains microbes that break down cellulose like
  rumen

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• Large colon absorbs nutrients released by cecum
• Small colon absorbs water and collects waste
• Rectum and Anus

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Chicken
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• Beak
• Prehension claws
• Mastication - no teeth and no enzymes in the
  saliva
• Esophagus
• Crop enlargement in esophagus that adds
  moisture
• Proventriculus adds HCl and enzymes to begin
  digestion

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• Gizzard muscular region that contains grit to
  grind food
• Small intestine absorbs nutrients through villa
• Ceca bi-lobed region that breaks down and
  absorbs cellulose not much in chicken diet
• Large intestine very short absorbs water
• Cloaca urine is combined with feces very high
  in N
• Vent homologous to the anus