Digestive Strategies

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Digestive Strategies
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What does your body use food for?

• Energy
• Raw materials

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Fuel Storage

• Glucose is major fuel
• Diet needs essential nutrients in addition to
  fuel

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Feeding Mechanisms

• Herbivores
• Carnivores
• Omnivores
• Suspension feeders
• Substrate feeders
• Fluid feeders
• Bulk feeders

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Types of Feeding
Filterfeed
Substrate
Fluid
Bulk
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Four stages of Food Processing

1. Ingestion
2. Digestion (uses enzymes)
3. Absorption
4. Elimination

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Strategy 1 Intracellular Digestion

• Lysosomes fuse with food vacuoles
• Digestion occurs within the cell
• Sponges are the only animal that digests food
  intracellularly

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Strategy 2 Gastrovascular Cavities

• digestive sacs
• Breakdown of food outside of cells
• Enzymes in cavity begin digestion

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Strategy 3 One way (tube) digestion

• Food moves from mouth to anus during processing
• Advantages
• Animals with one way digestion use stepwise
  processing
• Can eat more (dont have to wait for one meal to
  eliminate before starting the next)
• Due to advantages, animals with this strategy can
  be large and/or active!

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Human Digestive Compartments

• 21-30 feet long
• lined with mucus-coated cells
• Protection, enhances diffusion
• Mouth
• Saliva
• Salivary amylase breaks down carbos
• Water, buffers, mucins

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Human Digestive Compartments

• Pharynx start of peristalsis (muscle
  contractions)
• Epiglottis covers larynx
• Esophagus

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Human Digestive Compartments

• Stomach
• Muscular stretchy sac
• Functions
• Mixes and stores ingested food
• Digestion of proteins
• Enzyme (pepsin)
• 2L HCl daily activates enzymes

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Human Digestive Compartments

• Small intestines- Main digestive area (fats,
  carbos, and proteins)
• Pancreatic juice enters contains enzymes
• Bile (from liver) enters helps fat digestion
• Absorption, lined with villi and microvilli
• HUGE surface area!!

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Human Digestive Compartments

• Large intestines (colon)
• Concentrates and stores feces
• Absorption of water
• Contains bacteria
• Appendix (caecum)

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Mammalian Digestion

• Accessory glands
• Salivary glands
• Pancreas secretes enzymes
• Liver secretes bile
• Gallbladder stores bile

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