chapter 45 lecture
TRANSCRIPT
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Nutrition, Digestion &
AbsorptionChapter 43
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Nutrition
Nutrient
◦ Any organic or
inorganic substance
taken in that is
required for:
Survival
Growth
Development
Tissue repair
Reproduction
Nutrition
◦ The process of
consuming and
using food and
nutrients
Ingestion
Digestion
Absorption
Elimination
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Nutrition
Any nutritionally adequate dietsatisfies two primary purposes:
◦ 1) fuel (chemical energy)
◦ 2) raw organic materials (biosynthesis)
Homeostatic mechanismsmanage these resources.
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Nutrient Requirements
Organic
◦ Carbohydrates
◦ Protein
◦
Lipids◦ Vitamins
Inorganic
◦ Minerals
◦ Water
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5
Essential nutrients
Certain compounds cannot besynthesized from any ingested orstored precursor molecule
Must be obtained in diet
4 groups◦ Essential amino acids
◦ Essential fatty acids
◦ Vitamins
◦ Minerals
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Essential Amino Acids
8 Required
◦ Tryptophan, methionine, valine, threonine,
phenylalanine, leucine, isoleucine, lysine
Carnivores and omnivores readily
obtain all 8 in meat
Most plants do not contain every
essential amino acid in sufficient
quantity
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Essential Fatty Acids
Needed for membrane structure
Unsaturated fatty acids found primarily
in plants
Strict carnivores obtain them from fish
or adipose tissue of birds and
mammals
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Essential Vitamins
Organic nutrients that serve ascoenzymes◦ Water-soluble vitamins
vitamin C – not stored
◦ Fat-soluble vitamins vitamin A – stored in adipose tissue
Not all animals require the same vitamins◦ Only primates and guinea pigs can’t synthesize
vitamin C
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Vitamin C – Citric AcidVitamin A – Ascorbic
Acid
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Cofactor
◦ a non-protein
chemical compound
that is bound to a
protein and is
required for the
protein's biological
activity
◦ organic or inorganic
Coenzymes
◦ A cofactor that is
loosely bound
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Essential Minerals
Inorganic ions that serve as building
materials and cofactors
◦ Ca, P, S, K, Cl, Fe, Mg, Zn, I, Na
Many required in only trace amounts
◦ Less than 1 mg/day
Some can be stored
◦ Iodine or calcium
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Animals are Heterotrophs
Herbivores
◦ Plant material only
Carnivores
◦ Animal flesh and fluids
Omnivores
◦ Both plant and animal material
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Feeding Strategies
Suspension-feeders◦ baleen whale, bivalves, lancelet, tunicate
Substrate-feeders / grazers
◦ chiton, earthworm
Bulk-feeders
◦ Most carnivores, herbivores and
omnivores◦ python, lion, bear
Fluid-feeders
◦ mosquito, leech
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Ingestion
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Digestion
Chemical and mechanical breakdownof organic molecules into units small
enough for the body to absorb.
◦ Intracellular◦ Extracellular
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Intracellular
Intracellular
◦ Unicellularorganisms
◦ Sponges
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Extracellular – Gastrovascular
Cavity
Cnidarians
Flatworms
Mouth
Food
Food
Tentacle
Gastrovascular
cavity
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Extracellular – Complete Digestive
Tract
Alimentary Canal with specialized
regions
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Extracellular Digestion
Hydrolysis
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Absorption
Passive Diffusion
Facilitated Diffusion
Active Transport
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Summary
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Alimentary Canal
Divided into Functional Regions
Specialized for:
◦ Fragmentation
◦ Storage
◦ Grinding
◦ Chemical digestion – hydrolysis
◦ Absorption
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Vertebrate Digestive Tract
Mouth
Pharynx
Esophagus
Stomach◦ crop and gizzard
Small intestine
Large intestine
◦ (cloaca) Rectum
Anus
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Accessory Organs
Liver
◦ Produces bile
Gall bladder
◦ Stores bile Pancreas
◦ Produces gastric
enzymes
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Layers of the Gastrointestinal
Tract Mucosa
◦ Epithelial
Submucosa
◦ Connective tissue
◦ Nerves Muscularis
◦ Smooth muscle
Circular
Longitudinal Serosa
◦ Connective tissue
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Mouth
The tongue mixes foodwith saliva.◦ moistens and lubricates
food
◦ secretions controlled by
nervous system Taste-sensitive neurons inthe mouth send impulsesto the brain, whichresponds by stimulatingthe salivary glands.
◦ Antimicrobial
compounds◦ kills ingested bacteria
Initiation of chemicaldigestion polysaccharides
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Vertebrate Teeth
Carnivorous mammalshave pointed teeth thatlack flat grindingsurfaces.
Herbivores must
pulverize cellulose ofcell walls of planttissue beforedigestion.◦ have large, flat teeth
suited to grinding Humans are
essentially carnivoresin the front, andherbivores in the back.
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Pharynx and Esophagus
Swallowing centerstimulatessuccessive waves ofcontraction that
moves food alongesophagus tostomach. peristalsis
◦ Food entry is
controlled by ring ofsmooth muscle.sphincter
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Crop
Storage organ
Dilation of lower
esophagus
Little or nodigestion
Birds that eat
primarily grains
and seeds havelarger crops than
birds that eat
insects and worms29
Mouth:
Has no teeth and cannot grind food
Two parts of
the stomach—
Proventriculus:
Secretes acid
and enzymes
Gizzard:
Contains tiny pebbles
that help pulverize food
Intestine:
Digests and
absorbs food
Esophagus:
Moves food to
the crop by
peristalsis
Crop:
A dilation of
the esophagus
that stores and
softens food
Cloaca:
Receives undigested
material for excretion
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Stomach
Rugae◦ Surface is highly convoluted, enabling it to fold
when empty and expand as it fills with food.
Secretory systems
◦ Exocrine glands contain two cell types: parietal cells - secrete hydrochloric acid
chief cells - secrete pepsinogen
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Stomach
Acid
◦ Human stomach
produces about 2
liters of HCl and
other gastric juiceseveryday.
helps denature food
proteins
Chyme
Chyme
◦ leaves the stomach
through the pylorics hincter.
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Digestive Tract of a Ruminant
Multichambered
◦ Forestomach (3)
Microbes
cud
◦ True stomach
Extremely long
small intestines
Others◦ Cecum
Pouch at beginning of
large intestine
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Variation Based on Diet
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Small Intestine
Epithelial wall covered with villi
◦ covered by microvilli (brush border)
greatly increase surface area
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Accessory Organs
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Absorption
Glucose and amino acids enter thebloodstream via the hepatic portal
vein.
Fat enters the lymphatic system.◦ Vessel called a lacteal
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Absorption
Lumen
of
small
intestine
Protein Carbohydrate
Bile salts Emulsification
droplets
Free fatty
acids,
monoglycerides
Resynthesis
of triglycerides Triglycerides
+ protein cover
Chylomicron
Fat globules
(triglycerides)
Mono-
saccharides Amino
acids
Blood capillary (a) (b)
Lymphatic capillary
Epithelial
cell of
intestinal
villus
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Large Intestine
Concentratesundigested
material
◦
undigested material,primarily bacterial
fragments and
cellulose,
compacted and
stored
First Section
◦ cecum and
appendix,
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Large Intestine
Middle Section
◦ Colon
Ascending
Transverse
Descending
Final Section
◦ Sigmoid colon
◦ Rectum
◦ Anus