Download The Digestive System

The Digestive System
Functions
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Ingestion (eating)
Grinding
Digestion
Absorption of nutrients
Elimination of solid wastes
Introduction
• Digestive system changes food nutrients
into compounds easily absorbed by the
body
• Nutrients are used for:
– Energy, growth and maintenance
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
Digestive Tract
• Extends from the lips to the anus
• Length of digestive tract depends upon the
specie
– Carnivores is usually short, herbivores is long
• Simple and complex stomachs
Mouth
• Primary functions
– Prehension
• Grasping of food
– Grinding of feed
– Mixing feed and saliva
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
Tongue
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Used in prehension
Aids in chewing process
Mass of muscles covered by a membrane
Covered with papillae which contain the
taste buds
Lips
• Horses and sheep
– Used in grasping feed
– Used in sorting through feed
• Swine and cattle
– Keep mouth closed
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
Salivary Glands
• Common in the mucous lining of the
mouth
• Except for:
– Tongue
– Hard palate
– Gums
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
Esophagus
• Connects the pharynx to the stomach
• Walls have two layers of muscles
– Muscles run at right angles to each other
Non-Ruminant Stomach
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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
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
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
Ruminant Stomach
• Omasum
– Round in shape
– Contains many small papillae which grind
roughage
• Abomasum
– Only glandular stomach
– Similar to a non-ruminant stomach
Small Intestine
• 3 parts:
– Duodenum
• Digestive juices from pancreas and liver
– Jejunum
– Ileum
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
Poultry Digestive System
• Don’t have teeth
• Crop
– Stores and softens food
• Gizzard
– Grinds food
– Contains grit and gravel
• Proventriculus
– Glandular stomach
Pancreas
• Exocrine functions
– Produces digestive
juices
• Endocrine
– Produces insulin
Liver
• On the right side of
the body
• Purifies blood
Gallbladder
• Attached to the liver
• Produces bile
• Green organ