Digestive Excretory Circulatory Systems

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Digestive Excretory Circulatory Systems Powered By Docstoc
					Digestive, and Excretory
Did you know that
  your digestive
 system measure
  about 9 meters
long – from end to
                Before you start
• In a healthy diet you
  should have:
  –   Proteins
  –   Healthy Fats
  –   Vitamins
  –   Minerals
  –   Water
  –   Carbohydrates
       • Healthy sugars
       • Starches
       • Fiber
    3 Functions of the Digestive
1. Breaks down food into molecules the
   body can use = Digestion
2. Molecules are absorbed into the blood
   and carried throughout the body =
3. Wastes are eliminated from the body
            2 types of Digestion
• Mechanical Digestion            • Chemical Digestion
• Begins with your first bite     • Breaks down food with
  of food                           the help of enzymes – a
   – Teeth cut, slice and grind     protein that speeds up
     the food                       chemical reactions in the
   – Saliva makes it slippery       body
   – Swallow food to continue     • Each enzyme in the body
                                    has a specific function
                                     – Spit – contains an enzyme
                                       to break down starches into
                                       sugar molecules
                                     – Have a cracker
 Organs of the Digestive System -
• At the back of your mouth there are two
  – Epiglottis – a flap of tissue that seals off your
    windpipe when you eat
  – Esophagus – a muscular tube that connects your
    mouth to your stomach
     • Lined with mucus (a thick, slippery substance) that makes
       food easier to be swallowed
     • Food is in your esophagus for about 10 seconds.
     • Peristalsis – involuntary waves of smooth muscle contraction
       that pushes food to the stomach
           The Stomach
    A J-shaped muscular pouch.
 As you eat it expands to hold your
   food – average about 2 liters.
• Mechanical            • Chemical
  Digestion               Digestion –
   – 3 layers of          food is
     muscles contract     further
     to churn food        broken down
   – Similar to they      by digestive
     way a washing        juices –
     machine works –      produced by
     mixing the           cells lining
     contents with        the inside of
                          the stomach
           Digestive Juices
• Pepsin – enzyme that chemically digests
  proteins in your food
• Mucus – protects your stomach lining
• Hydrochloric Acid –
  – provides an acidic environment for the pepsin
    to function
  – Kills bacteria you swallow along with your
   Small Intestine – 6 meters long
                       • So now your food is a
                         thick liquid…it enters the
                         small intestine
                       • Starches and Proteins
                         have been broken
                         down…but fats haven’t
                       • Almost all chemical
                         digestion and absorption
                         of nutrients takes place
                         here…with help from the
                         liver and pancreas
Held together by the
         Help from the liver…
• Largest and heaviest
  organ inside your
• Produces bile (a
  substance that breaks
  down fat molecules)
• Bile moves from the
  liver to the gall
  bladder – stores bile
  until its needed in the
  small intestine
    Help from the Pancreas…
• Between the stomach
  and the small
• Produces 3 enzymes
  that continue the
  process of breaking
  down starches,
  proteins, and fat
Back to the small intestine
              • After chemical digestion –
                nutrients are absorbed
                into the villi of the small
              • Villi line the walls and
                contain blood vessels
              • The amount of villi greatly
                increases the surface
                area of the small intestine
                = greter absorption.
               What’s left?
• By now most nutrients have been
  absorbed – except fiber (thickens the
  liquid material in the intestines and allows
  it to be pushed forward)
• The liquid food also still contains water
• It is pushed by involuntary muscle action
  into the large intestine.
Large Intestine
     • A horseshoe shaped
       organ – 1.5 meters long
     • Contains bacteria that feed
       on the material passing
       through = make vitamin K
     • Water is absorbed into the
     • Remaining material enters
       the rectum and is
       compressed into solid
     • Waste is pushed out
       through the anus
Excretory System
    The Excretory System…
• …is the system
 of the body that
 collects wastes
 produced by
 cells and
 removes the
 wastes from the
 What is the waste that we need to
             get rid of?
1. Carbon Dioxide – more on this later with
   the respiratory system
2. Excess Water
3. Urea – a chemical that comes from the
   breakdown of protein

If your body didn’t take away these wastes,
    they would pile up and make you sick.
Organs of the Excretory System
• Kidneys – you have 2 of them – eliminate
  urea and excess water through urine.
  – As blood flows through the kidney they
    remove waste from the blood
  – Urine flows from the kidney through 2 narrow
    tubes called the ureters…..
  – To the urinary bladder – a sac-like muscular
    organ that stores urine
How do you know you have to go?
• When the bladder is full enough that its
  walls are stretched – you feel a need to
• Urine flows out of the body through a small
  tube called the urethra.
What do the Kidneys actually do?
                • Every drop of blood
                  travels through your
                  kidneys 300 times a
                • Your kidneys contains
                  about a million
                  nephrons – tiny
                  structures that
                  remove waste from
                  the blood and
                  produce urine
     Urine formation – 4 steps
1. Blood flows into a nephron
2. In the capillaries inside a nephron – urea,
   water, glucose, and other substances are
   filtered out of the blood. The filtered
   material passes into a capsule
   surrounding the capillaries
     Urine formation – 4 steps
3. From the capsule – the materials that
   were removed from the blood pass into a
   long twisting tube. As the filtered material
   flows through the tube – glucose and
   water are reabsorbed, urea stays in the
4. After the re-absorption is complete – the
   liquid that remains in the tube is urine.
         Urine and Disease
• What happens when you pee in a cup?
  – Normal urine contains no glucose or protien
  – Presence of glucose could = diabetes
  – Presence of protein = kidneys aren’t
    Why is water so important?
• Remember that as urine
  is being formed, water is
  absorbed back into the
  bloodstream. The amount
  absorbed depends on…
   – Hot day - Sweat a lot with
     little to drink – almost all of
     the water will be absorbed
     – little urination
   – Cool Day – Little Sweat
     with a lot to drink – less
     water will be absorbed –
     more urination

   – You need about 2 liters of
     water to maintain balance