chemical digestion by wuyunyi

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									             Chapter 3
 The Remarkable Body
Nutrition: Concepts & Controversies, 12e
              Sizer/Whitney
            Learning Objectives
 Describe the levels of organization in the
  body, and identify some basic ways in
  which nutrition supports them.
 Compare the terms mechanical digestion
  and chemical digestion, and point out
  where these processes occur along the
  digestive tract.
 Trace the breakdown and absorption of
  carbohydrate, fat, and protein from the
  mouth to the colon.
               The Body’s Cells

 Body is composed of trillions of cells
 Body needs nutrients
 Cells are self-contained, living entities
   Depend on one another
   Basic needs
      Essential nutrients
 Cells die at varying rates
A Cell (Simplified Diagram)
              The Body’s Cells

 Genes
   Control function
   Direct production of proteins
   Provide instruction for structural
    components of cells
   Affects how body handles nutrients
   Complete set of genes in each cell
 Tissues, organs, and body systems
From DNA to Living Cells
           The Body Fluids and the
           Cardiovascular System
 Body fluids
   Supply energy, oxygen, nutrients, and water
   Deliver fresh supplies and pick up wastes
 Types of fluids
   Blood
      Arteries, veins, capillaries
      Plasma
   Lymph
Blood Flow in the Cardiovascular
            System
           The Body Fluids and the
           Cardiovascular System
 Extracellular fluid
 Intracellular fluid
   All cell reactions
    take place
   Holds cellular
    shape
           The Body Fluids and the
           Cardiovascular System
 All blood circulates
  to the lungs
   Picks up oxygen
   Releases carbon
    dioxide
           The Body Fluids and the
           Cardiovascular System
 Blood returns to heart
   Blood pumped to rest of body
      Delivers nutrients
      Picks up wastes
 Blood passes through digestive system
   Picks up nutrients
      Except for fats
      Fats travel via lymph
   Routed directly to liver
Lymph Vessels and the
    Bloodstream
           The Body Fluids and the
           Cardiovascular System
 Kidneys
 Fluid intake
 Red blood cell life
  expectancy
 Blood is sensitive to
  malnutrition
        The Hormonal and Nervous
                System
 Hormones
   Chemical messengers
   Secreted and released directly into blood by
    glands
   Stimulate organs to take action
 Glands monitor conditions in the body
   Pancreas
      Insulin and glucagon
        The Hormonal and Nervous
                System
 Nutrition affects the hormonal system
   Hormones affect nutrition
      Appetite changes during pregnancy
 Nervous system
   Receives and integrates information from
    sensory receptors
   Role in hunger regulation
      Cortex and hypothalamus
  Cutaway Side View of the Brain
Showing the Hypothalamus & Cortex
         The Hormonal and Nervous
                 System
 Fight-or-flight reaction (stress response)
   Neurotransmitters
      Epinephrine and norepinephrine
   Metabolism speeds up
   Organ response
      Eyes, heart, liver, stomach
   Heart disease
           The Immune System

 Cooperation among tissues to maintain
  defenses
   Physical barriers
 Antigen
 Immune defenses
   White blood cells
     Phagocytes
     Lymphocytes (T-cells and B-cells)
            The Immune System

 Inflammation
   Response to injury or irritation
      Increased white blood cells, redness, heat,
       pain, swelling
   Normal and healthy response
   Problem with chronic inflammation
      Dietary factors
           The Digestive System

 Four basic chemical tastes
   Sweet, sour, bitter, and salty
   Savory
 Sweet, salty, and fatty foods
   Almost universally desired
   Can lead to drastic overeating of these
    substances
           The Digestive System

 Digestive tract
   Flexible, muscular tube
      Path
   Total length of about 26 feet
   Body surrounds digestive canal
 System’s job is to digest food to its
  components, absorb, and excrete
   System works at two levels
The Digestive System
           The Digestive System

 Chemical digestion
   Digestive juices
      Salivary glands, stomach, pancreas, liver,
       and small intestine
   Mouth
      Saliva – starches and fat
      Saliva – health of teeth
   Stomach
      Hydrochloric acid – protein
           The Digestive System

 Chemical digestion
   Intestine
      Bile
      Pancreatic juice
      Digestive enzymes in wall of intestine
      Fiber
 Food combinations and digestion
          The Digestive System

 Within 24 to 48 hours
   90% of carbs, fat, and protein are digested
    and absorbed
 Mouth
   Food is crushed, mashed, and mixed with
    saliva
   Carbohydrate digestion begins
   Swallowing
      Peristalic waves
            The Digestive System

 Stomach
   Gastric juice mixes with food
      Unwinds proteins
   Chyme
 Small intestine
   Bile from the liver
   Pancreas
 Large intestine
The Digestive System
          The Digestive System

 Absorption
   Nutrient molecules transverse intestinal
    lining
       Water-soluble components
       Fat-soluble components
   Cells of small intestine are selective
   Folded structure
       Villi
       Microvilli
Details of the Small Intestine
             Lining
           The Digestive System

 Transport
   Lymph vessels
      Products of fat digestion
      Fat-soluble vitamins
   Blood vessels
      Products of carbohydrate & protein digestion
      Most vitamins
      Minerals
 Nourishment of digestive tract
            The Excretory System
 Organs involved in waste removal
   Lungs, liver, kidneys
 Kidneys
   Waste materials are dissolved in water
   Working units – nephrons
   Urine is stored in bladder
   Sodium and blood pressure
   Work regulated by hormones
   Importance of water supply
              Storage Systems

 Eating intervals of 4-6 hours
 Major storage sites
   Liver – carbohydrates
      Glycogen
   Muscles – carbohydrates
      Glycogen
   Fat cells – fat and fat-related substances
 Variations in nutrient stores

								
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