Lab 8 Digestive System

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					Lab 8: Digestive System
   Exams

   Lab notes will be on reserve in library and
    on the web
Goals of the Digestive System
1.   Extract nutrients from food

2.   Transform nutrients into useful forms
      Ex- oreo= glucose

3. Absorb nutrients and distribute them
   where they are needed
     Functions of the Digestive
   Ingestion: intake of nutrients

   Digestion: breakdown of large particles into
    smaller ones

   Absorption: uptake of nutrient molecules

   Defecation: elimination of undigested residues
      Actions of the Digestive
1. Motility
      -   Breaks up food
      -   Moves food through the GI tract (Peristalsis)
      -   Mixes with digestive enzymes
2.   Secretion
      -   Release of enzymes and hormones for chemical
          digestion and regulation
3.   Membrane Transport
      - Absorption of nutrients from the tissues by the
        blood and lymph for transport
           Stages of Digestion
   Mechanical: physical breakdown of food

   Chemical: digestive enzymes hydrolyze food
    particles to break larger molecules into smaller

   Some nutrients are absorbed with out digestion
    – Vitamins, minerals, cholesterol, water
      Anatomy of the Digestive
   Oral Cavity
   Pharynx
   Esophagus
   Stomach
   Pyloric Sphincter
   Small Intestine
   Large Intestine
           Accessory Organs

   Teeth
   Tongue
   Salivary Glands

                         Liver
                         Gall Bladder
                         Pancreas
                     Oral Cavity
   Functions:
    – A.   Ingestion: cheeks lips
      and tongue mobilize food
    – B.   Digestion:
          Mechanical
            – Mastication
          Chemical
            – 3 salivary glands
            – Digests some
              starches and fat
    Motility: pharyngeal
     constrictors force food
     down during

   Straight muscular tube
    about 1 foot long
   Motility: muscular
    contraction moves
    food towards stomach
Heartburn and the Esophagus
Heartburn, “ acid reflux”, is caused by acid and food
  going from the stomach into the esophagus

The diaphragm normally prevents acid reflux, in
  conjunction with the lower esophageal sphincter.

When this fails, the burning sensation felt is known
 as “heartburn”

May be linked to a rare type of cancer,
       Muscular sac on the left
        side of the peritoneal

       Functions:
         – Food storage
         – Mechanical digestion
         – Chemical digestion
        Rugae in the Stomach

   Rugae- folds in the
    stomach lining that
    allow it to expand with
    more food

   How do we vomit?
             Pyloric Sphincter

   Ring of smooth

   Regulates the passage
    of material from the
    stomach into the
     Digestion in the Stomach
   Mechanical Digestion:
    – Muscular contraction

   Chemical Digestion:
    – Secretes digestive enzymes and HCl
                                   Small Intestine

                                                           2 meters long, 1 inch
                                                            in diameter, 5-6
                                                            meters in cadaver

                                                           Functions:
                                                            – Chemical Digestion
                                                            – Nutrient Absorption
                                                            – Motility
    Anatomy of the Small Intestine
    Duodenum (25 cm):           Fig 25.22
    1. Receives stomach
       contents, pancreatic
       juice and bile
    2. Neutralizes stomach
       acid and pepsin
    3. Pancreatic enzymes
       and bile take over
       chemical digestion
Anatomy of the Small Intestine
   Jejunum (2.5m)

   Ileum (3.6 m)
    – Reabsorbs bile acids
         Functions of the Small
   Motility: smooth muscle

   Digestion: chemical
    enzymes received from
    the pancreas, liver and gall

   Nutrient reabsorption:
    microvilli increase surface
Dynamic Human: Microvilli
                 Large Intestine
   Functions
    – Motility

    – Reabsorbtion of Water and Electrolytes

   Symbiotic bacteria
    – Synthesis Vitamins B & K
              Anatomy of the Large
                    Transverse Colon: right to left

Ascending Colon:                                      Descending Colon:
up the right side                                     down the left side

Cecum: sac on                                         Sigmoid Colon:
lower right side                                      S-shaped
           Anatomy of the Large

   Rectum: straight down
   Anal Canal: out the
   Appendix: hangs off
    – Important in Immunity
           Enzymes Involved in
           Chemical Digestion
   Saliva:
    – Amylase: breaks down starch
    – Lipase: breaks down fats when it enters the
          Low pH of the stomach activates the enzyme
       Enzymes Involved in
       Chemical Digestion
• Stomach:
  • Digestive chemicals-
     • HCL: activates enzymes, breaks up foods
     • Pepsin: digests proteins
     • Renin: digests milk
       Pepsin Formation
• Interactions between Cells
   • Chief Cells make pepsinogen
   • Parietal Cells make HCl
   • Pepsinogen is cleaved by HCl into Pepsin
Dynamic Human: Pepsin
        Enzymes Involved in
        Chemical Digestion
• Small Intestine
   • Two sources of

  • Liver and Gall bladder
  • Pancreas
      Enzymes Involved in
    Chemical Digestion in the
        Small Intestine
• Liver secretes bile that is active in the small
  • Bile: aids in fat digestion and absorption
        •Activates pancreatic enzymes
        •Synthesized from cholesterol
        •Bacteria in the small intestine use bilirubin to
          make your feces brown

• Gall bladder stores and concentrates bile
                Gall Stones
   What is a gall stone?

   How do they treat gall stones?

   How is the gall bladder removed?
         Enzymes Involved in
       Chemical Digestion in the
           Small Intestine
    Pancreas: secretes pancreatic juice
    1. Amylase: breaks down starch
    2. Lipase: breaks down fats
    3. Ribonuclease (RNAase): breaks down RNA
    4. Deoxyribonuclease (DNAase): breaks down
    5. Zymogens: inactive enzymes that activate in the
       small intestine
     Mechanism of Absorption
   Membrane Transport:
    – Nutrients pass through membrane surface
    – The greater the membrane surface area, the
      greater the amount of nutrients that can be
   Surface Area
    – Rugae
    – Microvilli
Final Destinations of Digestion
   Starches  bloodstream

   Fats  lymph vessels (lacteals)

   Proteins  bloodstream
Dynamic Human:
                Cat Dissection
   Be able to locate and       Also know accessory
    identify                     organs
    – Esophagus                  – Tongue
    – Stomach                    – Teeth
    – Small Intestine            – Gall Bladder
    – Large Intestine            – Liver
         Ascending colon
         Transverse colon

         Descending colon
   Review today’s material
    – Dynamic Human Overview

   Know cat anatomy

   Lab Practical II returned – well done!

   Next week – Endocrine!!!