Download Digestive System

Digestion: Obtaining &
Processing Food
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Herbivores = plant-eaters
Carnivores = meat-eaters
Omnivores = both plants and other animals
Digestion: Obtaining Food
Solid foods
substrate feeders
Filtering from water
fluid feeders
Digestion: 4 Stages
Digestion
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Mechanical Breakdown:
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Physically breaking food apart (teeth, tongue,
stomach, etc)
Chemical Breakdown:
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enzymes and secretions to break down
chemically
Digestion: Chemical Breakdown
Digestion: Protozoans
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Intracellular digestion with oral groove or
phagocytosis
Digestion
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Gastrovascular cavity vs specialized digestive
tract
Gastrovascular cavity: one opening
cnidarian & flatworms
Digestion: Alimentary Canal
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Most have alimentary
canal
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Tube running from mouth
to anus
divided into specialized
regions that process food
sequentially
Crop: stores food
Gizzard: grinds food
(especially if no jaws or
teeth)
Digestion: Human
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Alimentary Canal vs Accessory Organs
Digestion: Human
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Alimentary Canal
mouth, esophagus,
stomach, small
intestines, large
intestines, rectum,
anus
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Accessory Organs
salivary glands, liver,
gall bladder, pancreas
Digestion: Mouth
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Mechanical Digestion
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Chemical Digestion
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Teeth, tongue
Saliva moistens it
Salivary enzymes amylase begin breakdown of starch
Tongue pushes the chewed food into the
pharynx
Digestion: Esophagus
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Peristalsis:
muscle
contractions
pushing down
bolus (food)
Digestion: Stomach
Digestion: Stomach
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Stomach mixes food with gastric juice from
gastric glands
Gastric glands – make HCl, pepsinogen, mucous
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HCl activates pepsinogen (inactive enzyme) to form
pepsin (enzyme to breakdown protein)
HCl also kills germs
Mucous – lines & protects stomach walls
Chyme (partially digested food) enters
duodenum (beginning of small intestines via
pyloric sphincter
Digestion: Small Intestines
Digestion: Small Intestine /
Pancreas / Liver / Gall Bladder
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Most of chemical digestion and absorption take
place in small intestines
Pancreas
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Makes bicarbonate (HCO3-), base that neutralizes
stomach acid
Pancreatic enzymes digest polysaccharides, proteins,
nucleic acids, and fats
Bile (made in liver, stored in gall bladder)
emulsifies (mechanical breakdown) fat droplets
for attack by pancreatic lipase
Trypsin breaks down protein in base
environment
Digestion: Small Intestine
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Absorption by villi
Digestion: Large Intestines
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Absorption of
water
E Coli live in LI,
make Vitamin K
Undigested
material = feces
Digestion:
Evolutionary Adaptations
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Plant harder
to digest
than meat
because of
cellulose
Herbivores
have longer
digestive
tract
Digestion
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Cows have 4 stomach chambers to break
down cellulose