1. Nutrition and Digestion
Chapter 21

2. 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’

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

4. 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

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

6. Comparative Digestive Tracts
Length and adaptations of GI selected for by lifestyle
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

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

8. Digestive Cycle Food ingested into a mouth opening
Pushed into a pharynx or throat
Passes through an esophagus to a secondary structure
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 intestines
Undigested materials exit via the anus

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

10. Pharynx Esophagus and trachea Eating Breathing
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

11. Stomach 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)

12. Small Intestine 3 sections, only duodenum (1st) digests, rest absorbs
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

13. 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) control
Water reclamation inhibited by irritation  diarrhea
Peristalsis too slow  constipation

14. Digestive Ailments Acid reflux Gastric Ulcers Lactose intolerance
Backflow of chyme into esophageal opening = heartburn
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
WBC’s 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

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

16. 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 can’t be self made

17. Essential Nutrients Essential fatty acids: most diets provide ample
Essential amino acids: 8 of 20 AA’s needed for proteins
Can’t be stored, deficiencies affect others
Meat, eggs, milk, and cheese are ‘complete’ while plants aren’t
Vitamins and minerals
Disorders
Undernourishment from low caloric diet
Malnourishment from absence of 1+ essential nutrient
Overnourishment from consuming more calories than need

18. 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 B’s)
Fat-soluble excess build up in fat (Vitamins A, D, E, and K)
Minerals are inorganic (many)
(Table 21.18A and B)

19. Truth in Labeling
Vitamin and mineral supplements aim to guarantee recommended dietary allowances (RDA’s)
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

20. Weight Loss Plans Increased spending to market weight loss plans
Hasn’t resulted in thinner or healthier individuals
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 way
Gastric by-pass