Nutrition and Digestion

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
• 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
• 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
• 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

15
Livers 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 cant be
  self made

17
Essential Nutrients

• Essential fatty acids most diets provide ample
• Essential amino acids 8 of 20 AAs needed for
  proteins
• 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
  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 Bs)
• Fat-soluble excess build up in fat (Vitamins A,
  D, E, and K)
• Minerals are inorganic (many)
• (Table 21.18A and B)

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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

20
Weight Loss Plans

• Increased spending to market weight loss plans
• Hasnt 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