Nutrition and Digestion (PowerPoint) by liaoqinmei

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									Nutrition and Digestion
Animal Digestion

   Animals ingest food in a variety of
    ways
       Absorption feeders absorb through
        body surface
       Ingestive feeders eat living or dead
        organisms
Animal Digestion
   Ingestive feeders
    are classified as:

       Omnivores – ingest
        both plants and
        animals
       Herbivores – ingest
        plants
       Carnivores – ingest
        animals
Animal Digestion
   Ingestive feeders use different mechanisms:
       Substrate feeders – live in or on their food source
        (earthworms, caterpillar)
       Fluid feeders – obtain food by sucking fluids from a
        living host (mosquitoes, ticks)
Animal Digestion
     Bulk feeders –
      eating large
      quantities of food
      (humans)
     Suspension feeders
      – extract food
      particles from
      surrounding water
      ( scallops, whale)
Animal Digestion

   Food processing occurs in four
    stages:
    (1)   Ingestion – consume
    (2)   Digestion – mechanical and chemical
          breakdown of food (polymers into
          monomers)
    (3)   Absorption – nutrients enter body
    (4)   Elimination - excretion
                                             Small
                                         molecules

                    Pieces
                    of food                          Nutrient
                                                     molecules
                              Chemical breakdown     enter body
              Mechanical      (enzymatic hydrolysis) cells        Undigested
              breakdown                                           material

 Food



1 INGESTION           2 DIGESTION                3 ABSORPTION     4   ELIMINATION


                                                                                    Figure 21.2
Digestion Occurs in Compartments
(1) Gastrovascular
  Cavity – flagella Tentacle      Mouth

  integral to moving
  food and mixing
  with enzymes       Food
                     (Daphnia,
                                             Flagella

                     a water      Food
 Allows uptake of flea)          particle


  large prey           Gastro-

 Gastrovascular
                       vascular
                       cavity

  attached to mouth
                                  Digestion in
                                  food vacuole
Digestion Occurs in Compartments

(2) Alimentary Canal – tube
  connected to mouth and anus
 esophagus     crop    stomach     intestine      anus
  pharynx    storage   churn     absorption    elimination
   Esophagus
                    Stomach
          Gizzard                    Anus




                                               Esophagus
                                                      Stomach
                         Intestine                              Gizzard
        Crop
                                                                          Intestine
  Mouth     Gastric pouches

GRASSHOPPER                                 Mouth

                                                Crop

                                                                             Anus


                                            BIRD




                                                                                 Figure 21.3B (cont)
Human Digestive System

   Composed of two parts:
       Alimentary Canal – mouth, oral cavity,
        tongue, pharynx, and anus
       Digestive glands – salivary glands,
        liver, and pancreas
                             Oral cavity
Mouth
Tongue                       Pharynx
Salivary
glands

                                     Esophagus
           Liver
                   Stomach




                                       Pyloric
                                       sphincter
                                                   Stomach
Gall-
bladder
                         Small
Pancreas                 intestine          Small
                                            intestine
                         Large
                         intestine


 Rectum

                        Anus                            Figure 21.4
Human Digestion (oral cavity)

   Chemical Digestion (saliva) -
    glycoproteins protect lining of
    esophagus
       Lubricates solid food
       Buffers in saliva neutralizes food
        (sodas)
       Antibacterial agents
       Amylase – hydrolyzes starch
    Human Digestion (oral cavity)
                               TEETH

                               Incisors


                               Canine

                               Premolars

                               Molars



                               “Wisdom”
                               tooth
Tongue




Salivary
glands



Opening of a
salivary gland duct
Human Digestion (oral cavity)

   Mechanical Digestion (chew)
       Incisors – biting
       Canine – tearing (bladelike)
       Premolars/molars – crush/grind
       Tongue – moves bolus to back of oral
        cavity
Human Digestion ( oral cavity)
   Pharynx – entry of gases and food
       When breathing, epiglottis is up an
        esophageal sphincter is contracted. Air
        moves into the larynx (voice box)
        which is attached to trachea
        (windpipe).
       When eating, epiglottis is down and
        and esophageal sphincter is relaxed.
       Esophagus & larynx attached to
        pharynx.
              Human Digestion (oral cavity)

                                    Bolus of food
Tongue
                                    Epiglottis                              Epiglottis
                                    up                                      down
Pharynx


Larynx
                                    Esophageal      Larynx                                Larynx
                                    sphincter       up                                    down
          Trachea                                                           Esophagus
          (windpipe)                Esophagus


             Sphincter contracted                       Sphincter relaxed                Sphincter contracted




                                                                                                   Figure 21.6
Human Digestion (oral cavity)

   Esophagus – moves food from
    pharynx to stomach
   2 layers of muscle
     Circular muscle layer – constricts
      esophagus
     Longitudinal muscle layer – shorten
      esophagus
    Both circular/longitudinal layers creates a
      wavelike motion called peristalsis
Stomach


Circular                        Relaxed
muscle layer                    muscles
                                Circular       Relaxed
                                muscles        muscles
                                contract,
               Bolus of         constricting
               food             passageway
                                and pushing
                                bolus down
               Longitudinal
               muscles
               contract,
               shortening
               passageway
               ahead of bolus

               Stomach
Longitudinal
muscle layer
Stomach

   Holds up to 2 liters of food and
    water
   Gastric Glands
       mucous cells secretes mucus and
        protects lining of stomach
       cells in stomach replaced every 3 days
       parietal cells secrete HCl (changes
        pepsinogen into pepsin
       chief cells secrete pepsinogen
Stomach
   The gastric glands are located
    within the epithelial cells that lines
    the stomach
   Pits are located within stomach
    lining to allow entry of gastric juices
    into stomach
   Secretion of gastric juices are
    regulated by nerve signals &
    hormones
Stomach
   2 to 6 hours to empty after a meal
   Acid chyme – food and gastric juices
   Pyloric sphincter – separates stomach
    from small intestine
   Gastric ulcers – open sores in stomach
    lining caused by Helicobacter pylori; able
    to neutralize acid surrounding bacteria;
    loss of mucus resulting in bacterial
    infection leading to gastritis (eliminated
    by antibiotics/bismuth)
Small Intestine
   Most chemical digestion occurs here
   Nutrients absorbed into blood
   Longest organ of the alimentary
    canal
   Over 6 meters long; 2.5 cm wide
   Pancreas produces digestive
    enzymes and alkaline solution rich
    in bicarbonate; neutralizes acid
    chyme
Small Intestine

   Liver produces bile; bile salts digest
    fats
   Gall bladder stores bile until needed
    in small intestine
   Duodenum receives chyme from
    stomach and mixes with bile and
    digestive enzymes
Small Intestine

   Completes digestion of starches
    that began in oral cavity
   Completes digestion of protein that
    began in the stomach
   Nucleases secreted from pancreases
    digest DNA and RNA
   Fats are surrounded by bile salts
    (emulsification)
Small Intestine

   Lipase breaks down fat into glycerol
    and fatty acid chains
   Increased surface area allows
    greater absorption (villi & microvilli)
   Lymph vessels and blood capillaries
    surround villi and absorb nutrients
    which takes them to larger blood
    vessels and liver
Small Intestine

   Liver converts nutrients to suit body
    requirements (excess glucose into
    glycogen)
   Nutrients go to heart which are
    distributed into body
Large Intestine

   1.5 meters long & 5 cm wide
   At large and small intestine junction
    is a cecum with an attached
    appendix (prone to infection)
   Primary function – water absorption
   Causes ingested food to become
    more solid (feces)
Large Intestine
   Feces composed of indigestble plant
    fibers and bacteria
   E. coli produces valuable vitamins
    (biotin, folic acid, B & K vitamins)
   Rectum – terminal portion of colon;
    controlled by voluntary and
    involuntary sphincter
   Constipation – occurs by lack of
    exercise or not enough plant fiber
Adaptation of Animal Digestive System

   Omnivore & Herbivore
       have longer alimentary canal
       takes longer to break down plant cell
        wall
       longer absorption
       nutrients less concentrated in plants
        than meat
                                Small intestine



Small
intestine      Stomach




                Cecum




               Colon
               (large
               intestine)




   CARNIVORE                HERBIVORE             Figure 21.12A
Adaptation of Animal Digestive System

   Herbivore have special chambers to
    house cellulose digesting microbes
   Nutrients are absorbed but most are
    lost in feces
   Rodents eat feces
Intestine    3 Omasum    1 Rumen


                                    Esophagus




   Rumen
            4 Abomasum         2 Reticulum




                                                Figure 21.12B

								
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