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					Chapter 3: The Human
        Body
              Body Cells
 Form tissues
 Tissues form Organs
 Organs form Systems (e.g., digestive)
 Turnover
 Require nutrients
                Organelles
Cytoplasm
Mitochondria—Power plant
 Major site for energy production
Nucleus
 DNA
Endoplasmic reticulum - communication network
 Rough endoplasmic reticulum - protein synthesis
 Smooth endoplasmic reticulum -fat synthesis
           Four Types of Tissues
   Epithelial
       Lines the outside surfaces and external passages
   Connective
       Holds structures together
   Muscle
       Able to contract
   Nervous
       Transport nerve impulses
          Digestive System
Mouth to anus called the alimentary canal. 24 ft
  long.
Functions
 ingestion
 Propulsion
 Mechanical digestion
 Chemical digestion
 Absorption
 Defecation
              Communication
 Mediated  by the nervous system and the
  endocrine system
 Digestion of food occurs with the help of
     Short reflexes. Local sensors inside GI tract.
      Sensitive to stretch, PH, osmolarity
     Long reflexes. Sensors in the CNS
     Hormones. Produced by stomach, and SI in
      response to short reflexes.
         Structure of GI Tract
 Peritoneum. Protection, mobility and
  lubrication
 Blood supply. Supplied by the abdominal
  aorta. All blood from GI tract moves directly to
  liver via portal vein.
 Mucosa. Specialized cells to protect organs
  from disease. Secretes mucus.
 Muscles. Movement of organs. Peristalsis.
   The
 Digestive
 System
     mouth
salivary glands
  esophagus
    stomach
small intestine
large intestine
     rectum
      anus
   pancreas
  gallbladder
       liver
                   The Mouth
 Mastication
 Saliva
     Enzymes to help breakdown simple sugars
     Mucus to lubricate the food for easier swallowing
      (bolus)
     Lysozyme to kill bacteria
 Tongue
     Taste receptors
     Enzymes to help breakdown fatty acids
          The Esophagus
 Long  tube
 Connects pharynx to the stomach
 Epiglottis prevents choking
 Peristalsis, muscle contraction
 Lower esophageal sphincter
 Heartburn
             The Stomach
 Cardiac sphincter and pyloric sphincter
 Capacity of ~4 cups
 Secretion of acid, enzymes, and intrinsic
  factor
 Holds food for 2-4 hours
 Formation of chyme
 Mucus layer prevents autodigestion
Physiology of the Stomach
             Stomach Acid
 Destroys   activity of protein
 Activates digestive enzymes
 Partially digests dietary protein
 Assists in calcium absorption
 Makes dietary minerals soluble for
  absorption
           The Small Intestine
   Three parts
       Duodenum
       Jejunum
       ileum
 Villi projections are located on the folds
 Absorptive cells are located on the villi
 Increases intestinal surface area by 600x
 Rapid cell turnover
The Small Intestine
       The Large Intestine

 ~3  1/2 feet in length
 No villi or enzymes present
 Little digestion occurs
 Creation of SCFA
 Absorption of water, some minerals,
  vitamins
 Contains bacteria
 Formation of feces for elimination
                     Rectum
 Stool remains
 Stimulates elimination
 Muscle contraction
 Anal sphincters
     Internal-involuntary
     External-voluntary
 Movement Along the Intestine
 Peristalsis
     A ring of contraction propelling material along
      the GI tract
 Mass    movement
     Peristaltic wave that contracts over a large
      area of the large intestine to help eliminate
      waste
Movement
                                            Presence of food       Stomach
1. The presence of food in                  in the stomach

  the stomach and chyme
  in the duodenum                       Presence of chyme
  stimulate mass                        in the duodenum 1
  movement in the colon.                                                           Colon


2. Mass movements are                               2                   2
  integrated by the enteric
  plexus.                                       2                            2
                                                    Mass movements
                               Stimulates
3. They propel the contents    mass                            3
  of the colon toward the      movement         2                            2
  rectum.

4. The presence of feces in                                    4

  the rectum stimulates               Stimulation
  parasympathetic and                 of local           Feces
                                      defecation                            Stimulation of
  local reflexes that result          reflexes                              parasympathetic
  in defecation.                                                            controlled
                                                                            defecation
                                                               Rectum       reflexes
                                        Presence of food
                                        in the stomach


                                    Presence of chyme
                                    in the duodenum
                                                                 Colon



The presence of food in
the stomach and chyme in
the duodenum stimulate
mass movement in the       Stimulates           Mass movements
colon.                     mass
                           movement




                                          Rectum
                                           Colon




Mass movements are
integrated by the
enteric plexus.           Mass movements




                     Rectum
                                                        Colon




They propel the contents of the
                                       Mass movements
colon toward the rectum.




                                  Rectum
                                                                       Stomach


                                                                         Colon




The presence of feces in the
rectum stimulates
parasympathetic and local
reflexes that result in defecation.                 Mass movements




                                      Stimulation                    Stimulation of
                                      of local                       parasympathetic
                                      defecation        Feces
                                                                     controlled
                                      reflexes                       defecation
                                               Rectum                reflexes
                      Accessory Organs
   Pancreas. Both endocrine and
    digestive organ. Releases
    bicarbonate, enzymes that break
    down nutrients, and insulin and
    glucagon to control blood sugar.
   Gallbladder. Holds and excretes bile.
   Liver
        Receives all nutrients from the SE
        Produces bile
        Dismantles and assembles protein
        Metabolizes fat.
        Detoxifies drugs and alcohol
        Plays major role in metabolic pathways
          Circulatory System

 Heart and blood vessels
 Systemic circuit
 Pulmonary circulation
 Lymphatic system
 Blood
             Lymphatic System
 Contains   lymph
 Immune cells
 Passage for large
  particles like lipids
 Empties into veins
  leading to the heart
Nutrient Absorption
       Exchange of Nutrients
 Insert   Fig. 3-4

				
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