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The Digestive System
A Closer Look
Betcha didn’t know that…
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Your intestines are 7.5 metres long!
A horse’s intestines are 27 metres long!
Digestion from mouth to anus takes ~72 hrs!
In your lifetime, your digestive system may handle about 50
tons o’ food!
The average person eats about 1.4 kg of food per day!
1.5 litres of saliva are produced each day!
An adult’s stomach can hold about 1.5 litres!
Each day 11.5 litres of digested food, liquids and digestive
juices flow through the digestive system…but only 100mLs
are lost in feces!
QOTD – Label Me!
Answers
1.
2.
3.
4.
5.
6.
7.
8.
Tongue
Esophagus
Stomach
Duodenum
Pancreas
Ileum
Large Intestine
Rectum
Purpose:
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To enable the absorption of the nutrients needed
for growth, maintenance and repair
Types of Digestion
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As food travels down the
alimentary canal it must
be broken down into
monomers so that our
cells can use them.
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They need to be small
enough to pass through
the villi and into the
bloodstream.
Mechanical Digestion
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Chewing, Mixing,
Emulsifying
Done with the teeth
Peristalsis: Muscular
contractions move the
bolus (food ball) along
the digestive tract.
Chemical Digestion
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Performed by enzymes
Uses the process of hydrolysis to break down
polymers into monomers.
Question:
HOW DO WE KEEP FROM DIGESTING
OURSELVES??
Answer:
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Line the entire system
with mucus!!
Lined from the
cardiac sphincter to
the anus.
Where is there no
mucus?
Esophagus…Acid
reflux (heartburn)
Components of Digestion
Ingestion
= the taking in of nutrients
= enters by mouth
Digestion
= the breakdown of complex organic molecules into
smaller components by physical & chemical means
Mechanical – done by teeth, and stomach
Chemical – done by the mouth, stomach,
liver, gallbladder, pancreas, small & large intestine.
Break It Down Now!
Enzymes
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Carbohydrases break down ________
Peptidases break down… ________
Lipases break down…
________
Absorption
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The taking up of digested molecules into cells
Done by stomach, small intestine (villi), large
intestine
small intestine (villi)
Absorption
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The Small Intestine is designed to have a
large surface area.
The inner membrane is folded like a fan
The entire surface is covered with villi (villus)
Each villus is covered with microvilli
Absorption involves diffusion and active
transport
Anatomy of a Villus
Proteins
Microvilli
Capillary
Lacteal
BEFORE
DIGESTION…
Starches
TOO BIG!!
AFTER DIGESTION…
SMALL ENOUGH!!
Lipids
Water
Minerals
TO BLOOD
Water soluble vitamins
(B, C)
Glucose
Amino Acids
Glycerol
TO LYMPH
Fatty Acids
Fat soluble vitamins (A,
D, E, K)
Elimination
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The removal of waste from the body
Done by large intestine, rectum and anus
Control Mechanisms
Regulation through
feedback
 Done by hormones
(chemical messengers)
 Thermostat Example:
-Too hot, shuts down
-Too cold, starts furnace
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Digestion of Fats
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When fats enter the
duodenum, the
hormone CCK
(Cholecystokinia) is
released which causes
the gall bladder to
release bile.
Fats are emulsified
Acidic Chyme
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When acidic chyme
enters the small
intestine, the hormone
secretin is released
which causes the
pancreas to release
bicarbonate ions.
The acid is then
neutralized!
Blood Glucose Levels
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When glucose
enters the blood
stream, the
pancreas releases
Insulin.
Insulin stimulates
the storage of
glucose
(as
Glycogen, in the
liver)
Blood Glucose Levels CONT
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When blood glucose levels drop too low,
the pancreas releases Glucagon.
Glucagon stimulates the release of
glucose (from Liver) into the bloodstream
Blood Sugar Levels
Check out Page 270!
Digestive System Problems
1. Ulcer
 A sore wall of the
stomach (peptic) or
duodenum (duodenal)
 HCl creates a hole in
the mucous lining…acid
irritates muscles
 Caused by bacteria that
reduce amount of
mucous.
 Treated with antibiotics
Digestive System Problems
2. Cirrhosis of the Liver.
 Scar tissue in liver.
 Caused by excessive
alcohol consumption and/or
hepatitis virus.
 Results in jaundice (yellow
skin), nausea, pain, fluid in
abdomen
 Treatment…stop drinking!,
vitamins, transplant.
 Read Page 273!
Digestive System Problems
3. Inflammatory Bowel Disease
 Crohn’s Disease and
Ulcerative colitis
 Inflammation of the lining of
small or large intestine.
 Treatment: Drugs,
supplements or…
 Resection and Colostomy
 A stoma is created, and a
pouch collects the waste.
Digestive System Problems
4. Constipation
 Too much water is
removed from feces
 Usually because waste
is moving too
slowly…”bunged up!”
 Treatment: Eat fibre!
(cellulose), laxatives,
suppositories.
Time to get Active!!
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Using all the members of the class,
create a representation of the journey
of a peanut butter and banana
sandwich through the digestive
system from start to finish!
WE’RE DONE!!!