Intoduction

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					digestion

 Chapter
                  outline
•   Food processing overview
•   Digestive system
•   Nutrition requirements
•   Nutritional disorders
Digestive systems
     Digestive compartments
• Prevent digestion of own tissues
            Food processing
•   Ingestion
•   Mechanical processing
•   Secretion
•   Digestion
•   Absorption
•   Excretion
•   movement
       Nutrition introduction
• Heterotrophs
• Provides
 molecules body
Needs to function
                    ingestion
• Intake of food source
  ie organic & inorganic
  molecules
  – Food, water &
    minerals
• Physical action
      Mechanical Processing
• Physical process
• Physical reduction of food size
• Tongue, teeth, churning (mixing) of
  stomach & intestine
Mechanical Processing
Mechanical Processing
               secretion
• Production & release of digestive
  chemicals & enzymes
• Ex production of salivary amylase to
  chemically break down food particles
Mouth Watery goodness
Secretion
               digestion
• Break down of food
• chemical & enzymatic breakdown of
  ingested particles
• Absorbable units- monomers
  – Monosaccharides
  – Amino acids
  – Fatty acids
Chemical digestion
digestion
              absorption
• Transport of monomers through intestinal
  cells into blood & lymph
absorption
               excretion
• Removal of indigestible substances
• Defecation- removing solid wastes
excretion
               movement
• Transfer of ingested particles through the
  digestive tract
• Peristalsis
  – Wave-like smooth muscle contractions of the
    digestive tract
  – Pushes solids & liquids through tract
movement
peristalsis
           Digestive System
• Gastrointestinal tract
• Accessory organs
           Alimentary canal
• Aka gastrointestinal tract
• Tube within a tube design
• Gut & accessory organs
             Gastrointestinal tract
• Aka GI tract, ailimentary canal
• All regions food passes through
• Primarily composed of smooth muscle- involuntary
   – Excludes entrance & exit= skeletal muscle
• Continuous, open-ended muscular tube
   –   1 way
   –   Mouth to anus
   –   ~27 ft (8.2 m)
   –   Sphincters- regulation
• Organized into divisions
   – Specialized regions= different organs
   – Specializations result in specific isolated functions
Gastrointestinal Tract
27 feet!
Specialized regions of tube
          GI tract components
•   Oral cavity
•   Pharynx
•   Esophagus
•   Stomach
•   Small & large intestine (colon/rectum)
          Accessory organs
• Aid in food processing as it travels through
  the digestive tract
• Food does not pass through accessory
  structures
           Accessory organs
•   Teeth
•   Tongue
•   Salivary glands
•   Liver
•   Gall bladder
•   pancreas
Accessory organs
Accessory organs
             General Histology
• 4 tissue layers
• Aka tunics
   – Mucosa
      • Most variable
   – Submucosa
   – Muscularis
   – Serosa
      • Visceral peritoneum
• Variations in tunics reflect specialization of
  function
• Variations identify GI tract regions
         Tunics




Layers within tube system
             Tunics



 Mucosa




Submucosa


Muscularis

 Serosa
Tunics


         Mucosa
   Tunic variations




Mucosa most variable layer
       Generalized tunic structure
•   Mucosa
•   Submucosa
•   Muscularis externa
•   serosa
                      Mucosa
• Inner most layer of GI tract
• In contact with food
• Mucous membrane
  – 3 layers
     • Epithelium
     • Lamina propria
        – Connective tissue
     • Muscularis mucosae
        – Muscle tissue
         Mucosa epithelium
• Stratified &/or simple
  – Esophagus- stratified squamous
  – Stomach- simple columnar
• Glandular epithelium
  – Mucus- lubrication
  – Digestive- enzymes & chemicals
esophagus- stratified squamous
Stomach- Simple Columnar




     Secretion
Glandular Epithelium
Glandular Epithelium
               Lamina Propria
• Underlying loose areolar connective tissue of
  Mucosa tunic
• Contains blood & nerve tissue
  – Nutrients to epithelia
• Lymphoid tissue
  – Immune- white blood cell aggregations
  – Peyer’s patches
• Glands
  – Mucosal glands
  – Brunner’s glands
Lamina Propria
Lymphoid tissue
Glands
       Muscularis Mucosae
• External to lamina propria
• Narrow band of smooth muscle found in
  mucosa tunic
• Pushes GI tract into macroscopic folds
  – Rugae
• Increases surface area
Muscularis Mucosae
Rugae & Plica Circularis
       Generalized tunic structure
•   Mucosa
•   Submucosa
•   Muscularis externa
•   serosa
                  Submucosa
• Loose areolar ct
• Contains
  – Large blood vessels
  – Lymph tissue- especially in lower GI
  – Large glands- submucosal glands
     • Duodenal glands- aka Brunner’s Gland
        – Alkali mucus
     • Peyer’s patch aka Lymph nodule
        – Aggregations of immune cells
  – Nerves- control glandular secretions
     • Submucosal plexus
     • Meissner’s plexus
submucosa
submucosa
Submucosal Glands
Peyer’s Patch- Lymph Tissue
Meissner’s plexus
       Generalized tunic structure
•   Mucosa
•   Submucosa
•   Muscularis externa
•   serosa
               Muscularis Externa
• Comprise GI tract muscular wall
• Produces movement (peristalsis) & regulates passage
  (sphincters)
• Muscle type
   – Primary smooth muscle
        • Majority of tract unconscious control
• Skeletal muscle
   –   Sphincter
   –   Entrances & exits consciously controlled
   –   Mouth, pharynx, sup. Esophagus, external anal sphincter
   –   Myenteric plexus
• 2 layers of muscle
   – Circular layer- decreases diameter of tube
   – Longitudinal layer- changes length of tube
Muscularis Externa
Muscularis Externa
Muscularis Externa
external anal sphincter
                 Peristalsis
• Inner circular layer
  – Alters diameter of GI tract
• Outer Longitudinal
  – Alters length of GI tract
• Alternating contractions produce-
  peristalsis
    Inner Circular Layer




Diameter change
Outer Longitudinal




    Alters length
Alternating contraction
       Generalized tunic structure
•   Mucosa
•   Submucosa
•   Muscularis externa
•   serosa
                   Serosa
• Covering over GI tract
• Visceral peritoneum
• Function
  – Conduit for blood vessels & nerves
  – Attach & support: maintain position
• Composition
  – Primarily serous membrane
Serosa
Serosa
Serosa

				
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posted:3/4/2012
language:English
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