The Digestive System

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The Digestive System
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Functions

• Ingestion (eating)
• Grinding
• Digestion
• Absorption of nutrients
• Elimination of solid wastes

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Introduction

• Digestive system changes food nutrients into
  compounds easily absorbed by the body
• Nutrients are used for
• Energy, growth and maintenance

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Definitions

• Herbivores
• Depend entirely on plants for food source
• Ex. Cattle, sheep, horses, rabbits
• Carnivores
• Depend primarily on flesh of other animals
• Ex. Dogs and cats
• Omnivores
• Consume both flesh and plants
• Ex. Swine, poultry, humans

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Digestive Tract

• Extends from the lips to the anus
• Length of digestive tract depends upon the
  species
• Carnivores is usually short, herbivores is long
• Simple and complex stomachs

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? Ruminant System
Monogastric System ?
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Mouth

• Primary functions
• Prehension
• Grasping of food
• Grinding of feed
• Mixing feed and saliva

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Teeth

• Responsible for grinding
• Incisors are used for cutting food
• Premolars and molars are responsible for grinding
• Milk teeth
• Lost and replaced by permanent teeth

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Tongue

• Used in prehension
• Aids in chewing process
• Mass of muscles covered by a membrane
• Covered with papillae which contain the taste buds

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Lips

• Horses and sheep
• Used in grasping feed
• Used in sorting through feed
• Swine and cattle
• Keep mouth closed

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Other Mouth Parts

• Cheeks
• Lines food up with the teeth
• Jaw
• Lined with powerful muscles that aid in chewing
• Hard Palate
• Roof of the mouth
• Soft Palate
• Divides pharynx and oral cavity

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Salivary Glands

• Common in the mucous lining of the mouth
• Except for
• Tongue
• Hard palate
• Gums

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Pharynx

• Common passageway for air and food
• Several structures open into pharynx
• Mouth, nasal cavity, Eustachian tubes, larynx,
  and esophagus
• Pushes food into the esophagus

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Esophagus

• Connects the pharynx to the stomach
• Walls have two layers of muscles
• Muscles run at right angles to each other

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Non-Ruminant Stomach

• Consist of only one compartment
• Called the true stomach
• On the left side of the body
• High surface area due to folding
• Gastric glands produce
• Hydrochloric acid
• Enzymes
• Pepsin and rennin

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Ruminant Stomach

• 4 parts
• Rumen, reticulum, omasum, abomasum
• 1st three parts contain no glands, they soak food
  and allow for microbial digestion
• Reticulum
• Forward most portion
• Honeycomb-like

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Ruminant Stomach

• Rumen
• Fills most of the left side of the abdomen
• 2 parts dorsal and ventral
• Consist of two layers of smooth muscle
• Mature ruminants rumen accounts for 80 of the
  total stomach

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Ruminant Stomach

• Omasum
• Round in shape
• Contains many small papillae which grind roughage
• Abomasum
• Only glandular stomach
• Similar to a non-ruminant stomach

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Small Intestine

• 3 parts
• Duodenum
• Digestive juices from pancreas and liver
• Jejunum
• Ileum

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Large Intestine

• Consists of
• Cecum
• Shaped like a comma
• Varies drastically in size across species
• Horses and rabbits have largest ceca
• Blind pouch
• Colon
• Anus

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Poultry Digestive System

• Dont have teeth
• Crop
• Stores and softens food
• Gizzard
• Grinds food
• Contains grit and gravel
• Proventriculus
• Glandular stomach

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Pancreas

• Exocrine functions
• Produces digestive juices
• Endocrine
• Produces insulin

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Liver

• On the right side of the body
• Purifies blood

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Gallbladder

• Attached to the liver
• Produces bile
• Green organ

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ACTIVITY!!!