Animal Nutrition
With a side bar on the animal
kingdom!
Animal Phylogeny
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P.640 32.8
Why Digest?
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Makes food
available to cells
May be
intracellular-within
each individual cell
May be
extracellularenzymes are
released and food
is prepared for all
cells.
Intracellular is primitive
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Porifera Picture
Phylum
Porifera
Extracellular with one body opening
and gastrovascular cavity
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Cnidaria cross
section
Phylum Cnidaria
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Planaria cross
section
Phylum
Platyhelminthes
Extracellular with one way digestive
tract (have mouth and anus)
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Nematode Pix
Phylum Nematoda
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Annelids
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Annelid cross section
Phylum Annelida
Animals are group based on food
source
Carnivores- eat meatshorter intestine,
pointed teeth.
Omnivores- eat meat
and plants, teeth like
carnivore in front and
herbivore in back.
Herbivores- eat plants,
longer intestine, large
flat teeth to break up
plant tissue. Long
very specialized
digestive tract.
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Bear Pix
Herbivore modifications
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41.22
Specialized Actions
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Mechanical-teeth, grinding(pebbles
in bird and earthworm gizzards),
churning.
Chemical-hydrolysis by enzymes
• Ex:Salivary amylase
• Source-salivary gland
• Substrate-starch-a polysaccaride
• Product-maltose- a disaccaride
Human Digestive System
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Digestive System Pix
Food moves by
peristalsis
Accessory Organs
Liver-produces bile
Gallbladder-stores
and concentrates
bile
Pancreas-produces
pancreatic juice
(both enzymes and
bicarbonate)
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41.16
Stomach-Site of Protein Digestion
•Convoluted
•Secretes Gastric Juice-acidic
secretions of gastric glands of
mucosa
•Two cell types•Parietal-HCl
•Chief-pepsinogenactivated in low pH-to
form pepsin
•Low pH denatures proteins
•Protein digestion finished in
small intestine
•Output from stomach-chyme
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41.15
Protein Digestion
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41.18
Pepsin
Source-chief cells as pepsinogen
Substrate-protein
Product-polypeptides
Optimum pH-2
Trypsin
Source-pancreas as trypsinogen
Substratepolypeptide
Product-amino acids
Optimum pH-neutral
Small Intestine
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Carbohydrate, lipid,
protein digestion
finished.
Everything absorbed
(exceptions-aspirin,
alcohol, water absorbed in stomach)
First 25 cm-duodenumreceives secretions from
pancreas, gall bladder.
Then jejunum
Then ileum
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41.21
Structure of the GI Tract
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41.19
Inner mucosaepithelium
Submucosaconnective
Muscularis-double
layer of smooth
muscle
Serosa-more
connective tissue
SI Absorption
Brush Border-where a.a’s and
monosac’s are transported into
the epithelial cells, across
membranes and into blood
capillaries within the villi. From
here carried to the liver
Fat-hydrolyzed, absorbed,
reassembled into triglycerides.
Triglycerides combine with
protein to form chylomicronsabsorbed into lymphatic
system-empties into veins
near the neck.
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41.19
Large Intestine
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Large in diameter
Joins SI near two vestigial organs
• Appendix and cecum
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Vitamin K made by microorganism
here and absorbed.
Bacteria ferment here- produce gas
Low fiber diets-food moves slowlyassociated with high colon cancer
rates
Pancreas
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Secretes Pancreatic juice-enters duodenum
through the pancreatic duct. Contains
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Trypsin-protein
Chymotrypsin-protein
Pancreatic amylase-starch
Lipase-fat
Bicarbonate-neutralizes HCl makes alkaline
Secreted as zymogens-inactive enzymes
Activated by brush border enzymes
Digestion is completed by brush border enzymes
Liver
•Largest internal organ
•Secretes bile
•Bile pigment-from RBC’s-no digestive role-too much
jaundice
•Bile salts-work like detergent to emulsify
•Stored in gall bladder-fatty food triggers release
•Regulatory
•Metabolizes drugs, alcohol
•Removes steroid hormones
•Produces most blood proteins
•Regulates blood glucose-stored in liver as glycogen, used
up-does gluconeogenesis
Regulation of digestion
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Coordinated by nervous/endocrine
Sight/smell-nervous
Food in stomach-release of gastrin-causes
release of gastric juices
Hormones control passage of food into
duodenum-high fat slows passage
Duodenum secretes CCK in response to
fat-causes bile release
Secretin-causes pancreas to release
bicarbonate