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What is the purpose of the GI tract?
- Assimilation of nutrients
- Exclusion of unnecessary or harmful substances
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What are some common elements, principles, and processes of digestive physiology?
- Intake of food
- Digestion of nutrients from feed
- Absorption of nutrients
- Transport of absorbed nutrients to the site of metabolism and/or storage
- Excretion of waste products
- Ultimate goal is maintenance (survival)
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What are some differences in digestive physiology? (these are a matter of degree)
- Eating - specialized mouth structures
- Digestive tract
- Absorption of nutrients
- Metabolism of nutrients
- Excretion of waste products
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What is feces?
- unabsorbed nutrients
- non-nutrients
- bacteria
- sloughed cells
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What is urine?
- Absorbed nutrients and waste product
- Excretion of excess nitrogen
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What are the 3 different types of urine?
- Ureotelic - less H2O, urea = mammals
- Uricotelic - least H2O, uric acid = birds/reptiles
- Ammonotelic - most H2O, ammonia = fish
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What are the 3 types of GI tracts?
- Monogastric
- Non-ruminant herbivore
- Ruminant
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What are some properties of monogastric GI tracts?
- Simplest digestive system
- Relatively short
- Limited capacity (volume)
- Limited (variable) microbial action (fibre digestion)
- Adapted to use highly digestible diets
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What are some properties of non-ruminant herbivore GI tracts?
- Feeding requirements lie btwn monogastric and ruminant
- Functional cecum & large colon containing microbes
- Fermentation occurs after absorptive sections of GI tracts
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What are some properties of ruminant GI tracts?
- No upper incisor or canine teeth
- Four stomach compartments
- More space (volume)
- More microorganisms
- Fermentation occurs before absorptive surfaces
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What are the 4 stomach compartments in ruminants?
- Rumen (largest)
- Reticulum
- Omasum
- Abomasum (true stomach)
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What is the difference btwn non-ruminant herbivore fermentation and ruminant fermentation?
- Non-ruminant herbivore - hind gut fermentation
- Ruminant - Fore gut fermentation
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What are 2 microorganisms (microbes) and what role do they play?
- Fibre digestion
- Produce B vitamins and essential AAs
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