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Digestive System
Tooth Types
• Incisors
– biting & cutting food
• Canines
– tearing meat
– piercing & holding prey
• Premolars
– chewing, grinding soft food
• Molars
– chewing, grinding hard
food
Pre Molar or Molar?
Premolars: Bicuspid
(two cusps)
Molars: Quadrate (humans, some other
spp) Four cusps are arranged in a
rectangle; there may be a fifth.
Hypsodont: There is a lot of enamel and dentine above
the gumline and the top of the pulp. This kind of molar is
found in mammals that wear their teeth a lot, eg horse.
Parts of a Tooth
cement
Functions of Tooth Parts
• Enamel – covers crown, hardest
substance in body, made of calcium
phosphate
• Dentine – underneath enamel, harder
than bone
• Pulp cavity – nerves & blood vessels run
through this
• Cement – covers root, holds tooth in jaw
• Crown – part of tooth above gum
• Root – part of tooth in jaw (molars have
more roots than incisors)
How Many Teeth Do You Have?
• In humans, the first set (20
milk teeth) appear from age
six months to two and a half
years. The permanent
dentition replaces these from
the sixth year onwards, the
wisdom teeth (third molars)
sometimes not appearing until
the age of 25 or 30.
• Adults have 32 teeth: two
incisors, one canine (eye
tooth), two premolars, and
three molars on each side of
each jaw.
Dental Formula
“method of recording number and types of teeth in mammal jaws”
Lower Jaw
Upper Jaw
Upper
Lower
i2
2
c 1 pm 2
1
2
m3
3
x2 = 16
x2 = 16
total = 32
F
Pharynx
A
Tongue
G
Larynx
H
Oesophagus
B
Liver
IStomach
Stomach
Gall Bladder
C
Large Intestine (colon)D
Rectum
E
J
Pancreas
K
Small intestine
(ileum)
L
Anus
F
A
G
H
B
I
C
J
D
K
E
L
Digestion
“The breakdown of food into molecules small
enough to be absorbed into the blood”
• Physical Digestion: Mechanical
breakdown of food – chewing (mastication),
churning of food by stomach.
• Chemical Digestion: Enzymes + bile
chemically break food down.
Mouth
• Digestion starts here: food taken in:
ingestion
• Food chewed into smaller pieces
(physical digestion)
• Saliva moistens and lubricates the
food making it easier to swallow
• Saliva contains salivary amylase (an
enzyme) which chemically breaks
starch down to glucose (chemical
digestion)
• Salivary amylase is made by salivary
glands, works at a pH of 7 and is a
carbohydrase type of enzyme
• Tongue forms food into a ball shaped
“bolus” and is swallowed
Oesophagus
• Food pushed to stomach by wave of
muscular contraction behind the food this
is called peristalsis
(7s for food to get from mouth to stomach)
Oesophageal Peristalsis
http://www.nature.com/gimo/contents/pt1/fig_tab/gimo13_V1.
Oesophagus – Barrett’s Syndrome
Stomach
• Large muscular bag, churns and mixes food.
Food becomes a soupy mix called chyme.
• Acid (HCl) activates pepsin a protease enzyme
(enzymes that break protein down to amino
acids), produced by stomach wall, work best at
pH of 2
• Acid in stomach kills bacteria in food.
• Mucous stops the stomach digesting itself
• Water, alcohol and some food absorbed into
blood here
• Food stored for ~4 hours
Haggis
• Made of sheep's
or calf's heart,
lungs, liver
minced with
oatmeal onions
and boiled in the
animal's stomach
Stomach Gurgles
aka borborygmi
Causes:
1 In stomach / upper small intestine as muscles contract
to move food and gastric / digestive juices along
(normal!)
– Intestinal housecleaning?
– Happens most several hours after eating – this is why stomach growling
is associated with hunger.
2 Can also happen when incomplete digestion of food
causes gas (eg in lactose intolerance, coeliac disease
(gluten))
3 Caused by disease … include carcinoid neoplasm and
celiac sprue.
Small Intestine
• Bile is added (breaks down fat, neutralises
stomach acid so other enzymes can work, gives
faeces brown colour)
• Pancreatic enzymes added (break down
proteins, carbohydrates)
• Soluble food passes across small intestine wall
into blood: absorption
• Villi (finger-like projections increase surface area
for absorption)
• Peristalsis continues, forcing food along
• 7 metres long, 2.5-3 cm wide
Video Clips
• Small Intestine Endoscopy:
http://www.youtube.com/watch?v=Ln09qihUi3g
• Worm in Small Intestine:
http://www.youtube.com/watch?v=EXuoOWb8b
Gg
• Tapeworm Segment:
http://www.youtube.com/watch?v=3uk_aCZxmW
Y&feature=related
• Roundworm in cat intestine
http://www.youtube.com/watch?v=dB0cL3PcYZI
&feature=related
Small intestine of a domesticated pig, hanging at a market in Manila.
Peristalsis in horse intestine
Villi
*Extra Guts For Experts
Small Intestine
Size and Area
• The small intestine in an adult human measures on
average about 5 meters (16 feet), with a normal
range of 3 - 7 meters; it can measure around 50%
longer at autopsy because of muscle relaxation after
death. It is approximately 2.5-3 cm in diameter.
• CALCULATE THE AREA
Area = circumference x length
= pi x d x l
= 3.141 x 2.75 x 500
= 4319cm2
= 43m2
• Although as a simple tube the length and
diameter of the small intestine would have
a surface area of only about 0.5m2 or
50cm2, the surface complexity of the inner
lining of the small intestine increase its
surface area by a factor of 500 to
approximately 200m2, or roughly the size
of a tennis court.
*Extra Guts For Experts - Small Intestine
Parts of Small Intestine
• Duodenum 26 cm long. Breakdown of food, using enzymes.
• Jejunum 2.5 m. Absorption of food
• Ileum 3.5 m. Absorb vitamin B12 and bile salts and whatever
products of digestion were not absorbed by the jejunum.
* Cystic Fibrosis
• Inherited genetic disease – symptoms include
excess mucous production in lungs, gut
• Prevents pancreatic enzymes reaching small
intestine.
• SOLUTION?
• Oral enzymes
• SOURCE?
• Pigs
– more issues…
Large Intestine
• Water & minerals
absorbed, pass into
blood
• Remaining insoluble
food passes to rectum
• 1.5 metres long, 6 cm
wide
From Greys Anatomy pub. 1918
Appendix
• No CLEAR function in
humans
• BUT some suggestion
that the appendix may
harbour and protect
bacteria that are
beneficial in the function
of the large intestine
• In some herbivores
bacteria in the appendix
break down cellulose
• About 10cm long 7-8mm
wide
Appendix
Rectum
• Temporary storage for faeces.
• When full the nervous system triggers
need to defecate.
Anus
• Function: expelling
faeces (egestion or
defecation)
Liver
• Assimilation: Food molecules
packaged & stored for use in cells
(energy, growth, repair)
• Produces bile (helps breaks down fat
& is stored in gall bladder)
• Breaks down toxins (eg alcohol)
! The only internal human organ
capable of natural regeneration of lost
tissue; as little as 25% of a liver can
regenerate into a whole liver
How long does it take for a
damaged liver to repair itself?
• The liver is a unique organ. It is the only organ in the body that is able to
regenerate... that is completely repair the damage. With most organs, such
as the heart, the damaged tissue is replaced with scar, like on the skin. The
liver, however, is able to replace damaged tissue with new cells. An extreme
example is a patient who suffers an overdose from Tylenol. In this example
up to 50 - 60 percent of the liver cells may be killed within 3 - 4 days.
However, if no other complications arise, the patient's liver will repair
completely, and a liver biopsy after 30 days will appear completely normal
with no signs of damage and no scar. However, the long-term complications
of liver disease occur when regeneration is either incomplete or prevented
by progressive development of scar tissue within the liver. This occurs when
the damaging agent such as a virus, a drug, alcohol, etc., continues to attack
the liver and prevents complete regeneration. Once scar tissue has
developed it is very difficult to reverse that process. Severe scarring of the
liver is the condition known as cirrhosis. The development of cirrhosis
indicates late stage liver disease and is usually followed by the onset of
complications.
A liver riddled with multiple secondary cancer deposits
Pancreas
• Produces enzymes
that breakdown
carbohydrates, fat,
proteins. These are
secreted into the small
intestine.
• Also: produces
hormones such as
insulin which control
blood sugar levels.
Sweetbreads (on mushroom risotto)
Enzymes:
•
•
•
•
•
are chemicals
are protein
are not living
don’t eat
speed up chemical reactions (eg digestion)
They don’t look like this
They look like this
Pepsin
Enzymes
Group of enzyme
Example
Site of production
Substrate
Products
Optimum pH
Amylase
Salivary
Gland /
Pancreas
Starch
Glucose
7
Proteases
Pepsin
Stomach
Wall
Protein
Amino Acids
2
Lipases
Lipase
Pancreas
Lipids
Glycerol +
Fatty Acids
8
Carbohydrases
Kiwifruit vs Agar
Task: Place a slice of kiwifruit on some agar. Leave it for 10min.
Observe.
Copy & Complete:
Kiwifruit vs Agar
Observations before:
Observations after:
Inferences:
A method to test our inferences:
Q: Why Won’t Pineapple and Jell-O
Be Friends?
• A: If Jell-O™ ads and 1950s cookbooks are to be
believed, you can mix almost anything with gelatin and
have it come out tasty. Ham? Absolutely. Carrots? Sure
thing. Tomato soup? M’m, m’m, good.
• The only ingredient that seems to be taboo is the one
that actually sounds delicious: fresh pineapple.
Unfortunately, the tropical treat works like kryptonite on
Jell-O because it contains an enzyme called bromelain,
which prevents gelatin from forming into a solid. But fret
not, fruit salad and mold fans: canned pineapple doesn’t
contain bromelain. The canning process heats the
pineapple to a temperature sufficient to break the
enzyme down, making it oh-so Jell-O friendly.
Source: http://blogcritics.org/tastes/article/q-why-wont-pineapple-and-jell/
More on Enzymes
• Caromello!!
Digestion Summary
What
Where
How
Ingestion
Mouth
Food taken into body
Digestion
Gut
Food broken into pieces small
enough to be absorbed into the
blood
Food molecules cross gut wall into
the blood
Absorption
Stomach,
Small
Intestine
Assimilation Liver
Food molecules enter cells and are
used for energy, growth, repair
Egestion
Anus
Undigested food (+ bacteria) leaves
the body as faeces
Digesting Starch Experiment
• “Experiment 2” – Pg 258, Science World 9
•
•
•
•
Copy Title, Aim.
Read Method, get started  label carefully
Copy Method diagrams
Record results in a table
HEALTH WARNING! Only touch your own saliva –
clean up thoroughly!
Questions & Conclusions
1. State:
– Independent variable
– Dependent variable
– Controlled variables
2. How do the results show the action of saliva on
starch?
3. Why were tubes 1 & 2 included?
Model Intestines Experiment
• Turn to “Experiment 3” – Pg 261, Science World 9
– Discuss, set up experiment (label carefully!)
• Copy: Title, Aim
• Copy: the Method diagram after step 6 (label it!)
• Record results in a table
• Do the Questions & Conclusions (1-3 only).
– FULL answers or copy the question
Questions & Conclusions
1. State:
– Independent variable
– Dependent variable
– Controlled variables
Experimental Plan
Does salt (sodium chloride) pass across membranes? Use
what you have learnt from the Model Intestine
experiment to design a test to investigate this question.
Write…
Title
Aim
Hypothesis
Variables
- Independent
- Dependent
- Controlled
Equipment
Method
Digestive System Summary Task
• You are Horace the Hamburger and you are going to be eaten
and digested!
• Your task is to produce a large poster about your journey
through the digestive system and show how you get digested
along the entire journey. As you are a hamburger you must
account for the digestion of these nutrients:
–
–
–
–
Carbohydrate - starch (bun)
Protein (meat pattie)
Carbohydrate - cellulose (lettuce)
Lipids (fat)
• Conditions:
– Time allowed:
– Due Date:
– Fomat:
Teeth
Different Guts…
Notes Pages
F
A
G
H
B
I
C
J
D
K
E
L
Digestion
“The __________ of food into molecules small
enough to be absorbed into the blood”
• ________ Digestion: Mechanical breakdown of
food – chewing (mastication), churning of food
by stomach.
• _________ Digestion: Enzymes + bile
chemically break food down.
Mouth
• Digestion starts here: food taken in:
______
• Food chewed into smaller pieces (physical
digestion)
• Saliva m_______ and l_________the food
making it easier to swallow
• Saliva contains s_________ a_______ (an
enzyme) which chemically breaks
s________down to g_________ (chemical
digestion)
• Salivary amylase is made by salivary
glands, works at a pH of ______ and is a
c_________________type of enzyme
• Tongue forms food into a ball shaped
“b__________” and is swallowed
Oesophagus
• Food pushed to stomach by wave of muscular
contraction behind the food this is called
p_________________
(7s for food to get from mouth to stomach)
Oesophageal Peristalsis
http://www.nature.com/gimo/contents/pt1/fig_tab/gimo13_V1.html
Stomach
• Large muscular bag, churns and mixes food. Food
becomes a soupy mix called c_______.
• Acid (HCl) activates p_____ a p_______ enzyme
(enzymes that break protein down to amino acids),
produced by stomach wall, work best at pH of ____
• Acid in stomach kills b_______ in food.
• M_______ stops the stomach digesting itself
• Water, a_____ and some food absorbed into blood
here
• Food stored for ~____ hours
Small Intestine
• B____ is added (breaks down f_____, neutralises
stomach acid so other enzymes can work, gives
f_____ brown colour)
• Pancreatic enzymes added (break down p______,
c_________________)
• S______ food passes across small intestine wall into
blood: absorption
• Villi (finger-like projections increase surface area for
absorption)
• Peristalsis continues, forcing food along
• 7 metres long, 2.5-3 cm wide
*Extra Guts For Experts
Small Intestine
Size and Area
• The small intestine in an adult human measures on
average about 5 meters (16 feet), with a normal range of
3 - 7 meters; it can measure around 50% longer at
autopsy because of muscle relaxation after death. It is
approximately 2.5-3 cm in diameter.
• CALCULATE THE AREA
*Extra Guts For Experts - Small Intestine
Parts of Small Intestine
• Duodenum 26 cm long. Breakdown of food, using enzymes.
• Jejunum 2.5 m. Absorption of food
• Ileum 3.5 m. Absorb vitamin B12 and bile salts and whatever
products of digestion were not absorbed by the jejunum.
Large Intestine
• Water & minerals
absorbed, pass into
blood
• Remaining insoluble food
passes to rectum
• 1.5 metres long, 6 cm
wide
Rectum
• Temporary storage for faeces.
• When full the nervous system triggers need to
defecate.
Anus
• Function: expelling
faeces (egestion or
defecation)
Liver
• Assimilation: Food molecules packaged &
stored for use in cells (energy, growth,
repair)
• Produces bile (helps breaks down fat & is
stored in gall bladder)
• Breaks down toxins (eg alcohol)
! The only internal human organ capable of
natural regeneration of lost tissue; as
little as 25% of a liver can regenerate into
a whole liver
Pancreas
• Produces enzymes that
breakdown
carbohydrates, fat,
proteins. These are
secreted into the small
intestine.
• Also: produces
hormones such as
insulin which control
blood sugar levels.
Enzymes
Group of enzyme
Example
Site of production
Amylase
Salivary
Gland /
Pancreas
Proteases
Lipases
Stomach
Wall
Lipase
Substrate
Products
Optimum pH
Glucose
7
Protein
Lipids
2
Glycerol +
Fatty Acids
Digestion Summary
What
Where
How
Mouth
Digestion
Absorption
Food broken into pieces small
enough to be absorbed into the
blood
Stomach,
Small
Intestine
Liver
Food molecules enter cells and are
used for energy, growth, repair
Anus
Undigested food (+ bacteria) leaves
the body as faeces