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Nutrition and Digestion


Nutrition and Digestion Chapter 21 – PowerPoint PPT presentation

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Title: Nutrition and Digestion

Nutrition and Digestion
  • Chapter 21

Obtaining Food
  • Animals differ in dietary types
  • Herbivores eat autotrophs (plants)
  • Carnivores eat other animals
  • Omnivores eat plants and animals
  • Animals differ in how food is ingested
  • Suspension feeders filter food from water
  • Substrate feeders eat through a substrate
  • Fluid feeders sucking fluids
  • Bulk feeders ingest large pieces of food, using
    various utensils

Processing Food
  • Ingestion act of eating
  • Digestion breaking down food into absorbable
  • 2 stages
  • Mechanically
  • Chemically (Polymers to monomers)
  • Compartmentalized so only food, not self, is
  • Absorption cells in digestive tract take up
    digested products
  • Blood transports
  • Excess intake converted to fat
  • Elimination undigested material is excreted

Variability of Animal Digestive Tracts
  • Phago-/Pinocytosis
  • Gastrovascular Cavity
  • Entirely intracellular digestion
  • Form food vacuoles
  • Lysosomes break down
  • Sponges only examples
  • Extracellular digestion starts
  • Single opening
  • Enzymes into cavity
  • Ends intracellularly
  • Phago-/pinocytosis for by products
  • Also circulatory
  • system

Complete Digestive Tract
  • Entirely extracellular digestion
  • Two openings
  • Nutrients absorbed for use
  • Specialized organs for each stage
  • Most animals

Comparative Digestive Tracts
  • Length and adaptations of GI selected for by
  • Herbivores omnivores longer than carnivores
  • Herbivores lose many nutrients to feces
  • Recycle feces to regain
  • Specialized mircobes in cecum
  • Ruminants (cattle, goats, deer, etc.)
  • 4 chambered stomachs
  • Regurgitate food from 1st 2 to 2nd 2 chew cud

Mammalian Digestive System
  • Alimentary canal structures
  • Accessory glands (green) secrete digestive juices
  • Peristalsis moves food
  • Regulated by sphincters
  • Time varies at each stage

Digestive Cycle
  • Food ingested into a mouth opening
  • Pushed into a pharynx or throat
  • Passes through an esophagus to a secondary
  • Crop pouch like organ to soften and store food
  • Stomach and gizzard mechanical processing
    churns and grinds food some storage
  • Chemically digested and nutrients absorbed in the
  • Undigested materials exit via the anus

  • Sight, smell thought initiate
  • Saliva protects and lubricates
  • Salivary amylase, mucins, bicarbonate, and
  • Chemical digestion starch to maltose
  • Food presence maintains
  • Specialized teeth to mechanically breaks down
  • Tongue mixes/manipulates
  • Taste
  • Bolus formation

  • Esophagus and trachea
  • Mouth and nasal cavity cross
  • Regulation interruption and the Heimlich maneuver
  • Eating
  • Epiglottis covers trachea
  • Esophageal sphincter relaxes
  • Peristalsis moves food (voluntary muscles)
  • Lined with stratified squamous cells
  • Breathing
  • Trachea open
  • Esophagus closed
  • Heimlich maneuver

  • Prevent needs for constant feeding
  • Stores and mixes food
  • Gastric juices for chemical digestion
  • Sight, smell, and/or taste stimulates production
  • Pepsin breaks down protein
  • Stomach protection
  • Pepsinogen converted to pepsin (HCl trigger)
  • Epithelial replacement (3 days)
  • Positive and negative feedback mechanisms
  • Bolus into chyme
  • Sphincter controls small, regular release to
    small intestine (SI)

Small Intestine
  • 3 sections, only duodenum (1st) digests, rest
  • Fat digestion started
  • Liver produces bile, stored in gall bladder
  • Other molecules finished
  • Pancreas secretions to neutralize chyme and
    assist breakdown
  • Villi with microvilli to increase surface area
  • Absorption into blood (diffusion)
  • Peristalsis moves

Large Intestine (Colon)
  • Joins to small intestine
  • Cecum with attached appendix
  • Absorbs water, salts, and minerals
  • Moves via peristalsis
  • Solids left are feces
  • Indigestible plant fibers, bacteria (E. coli),
    and dead cells
  • Stores in rectum until elimination
  • Two sphincters (voluntary and involuntary)
  • Water reclamation inhibited by irritation ?
  • Peristalsis too slow ? constipation

Digestive Ailments
  • Acid reflux
  • Backflow of chyme into esophageal opening
  • Lifestyle changes
  • Pepcid AC, Zantec, and Prilosec slow or limit
    acid production
  • Gastric Ulcers
  • Corrosive effect of gastric juices (old)
  • Helicobacter pylori to blame (new)
  • Loss of mucus and destroy cells
  • WBCs attack H. pylori mild inflammation
  • Can reach a point where a hole develops
  • Lining destroyed faster than replaced
  • Lactose intolerance
  • Lactase absence in SI
  • Bacteria in LI ferment sugar

Livers Role
  • Key in regulating metabolism
  • Direct transport of nutrients from SI and LI
  • Removes excess glucose converts to glycogen for
  • Coverts substances into new, essential proteins
  • Modifies and detoxifies
  • Inactive products released in urine
  • Urine tests
  • Excess can cause damage

Nutritional Needs
  • Same for all animals, regardless of diet
  • Fuel for all activities
  • Organic molecules to build own molecules
  • Carbohydrates
  • Fats
  • Lipids
  • Water
  • Essential nutrients are substances that cant be
    self made

Essential Nutrients
  • Essential fatty acids most diets provide ample
  • Essential amino acids 8 of 20 AAs needed for
  • Cant be stored, deficiencies affect others
  • Meat, eggs, milk, and cheese are complete while
    plants arent
  • Vitamins and minerals
  • Disorders
  • Undernourishment from low caloric diet
  • Malnourishment from absence of 1 essential
  • Overnourishment from consuming more calories than

Vitamins and Minerals
  • Tiny amounts needed, but deficiency can cause
    serious complications
  • Excess can be problematic too
  • Vitamins are organic (13 )
  • Water-soluble excess excreted in urine (Vitamin C
    and Bs)
  • Fat-soluble excess build up in fat (Vitamins A,
    D, E, and K)
  • Minerals are inorganic (many)
  • (Table 21.18A and B)

Truth in Labeling
  • Vitamin and mineral supplements aim to guarantee
    recommended dietary allowances (RDAs)
  • Levels are debated
  • Varies with age and sex
  • Ingredients listed most to least amounts
  • High fructose corn syrup
  • Whole wheat vs enriched wheat flour
  • Food serving size and energy content (calories)
  • Emphasize nutrients related to disease and
    healthy diets

Weight Loss Plans
  • Increased spending to market weight loss plans
  • Hasnt resulted in thinner or healthier
  • Trends in dieting often repeated
  • New fad diets introduced intermittently
  • Can trade one problem for another
  • Initial results from water loss
  • Problems in maintenance
  • Healthy lifestyle and eating only 100 effective
  • Gastric by-pass
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