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The Human
Digestive System
What do you already know?
• Complete the Digestive System Handout
to the best of your ability without looking
in any text or your notes.
• You may work in groups.
• Do not complete the bottom overview.
The Human
Digestive System
Video Overview
Why do we need a Digestive System?
When you eat foods such as
bread, meat, and vegetables,
they are not in a form that the
body can use.
Food and drink consumed must
be broken down into smaller
molecules so that they can be
absorbed into the body.
Components of the Digestive System?
• The Digestive Tract is a series of hollow
organs joined in a long, twisted tube
from the mouth to the anus.
• Organs involved:
Small Intestine
Large Intestine
Components of the Digestive System?
• The entire length of the digestive tract is
lined with epithelial tissue.
• Contains lots of goblet cells which secrete
mucus. The mucus does two things
1. Protects tract from digestive enzymes
2. Moves materials along the tube
Digestive Enzymes
• Digestive Enzymes help to break
food into smaller pieces so that
it is easier to digest
Digestive Enzymes Video
The Mouth
• Digestion begins in the oral cavity
(mouth) where 2 types of digestion
take place:
1) Mechanical Digestion
2) Chemical Digestion
Mechanical Digestion
• Chewing breaks up large
pieces of food into smaller
Chemical Digestion
• The Human Body releases 1 – 1.5L
of saliva per day from glands in your
cheeks (salivary glands)
• Saliva converts Carbohydrates
into simple sugars like Glucose.
Chemical Digestion
• Saliva also contains mucus and
water which makes food easier to
Chewing Crackers Activity – Part 1
Put a regular cracker into your
mouth and chew
What did it taste like?
• Sweet? Plain? Record your
Chewing Crackers Part 2 – Record your
Place a cracker in your mouth and let it sit for 1.5 min.
before chewing
What it feels like initially
in your mouth
- Is it sweet/bland?
What is feels like after 1
min. in your mouth
- Is it sweet/bland?
What it feels like after
1.5 min. in your mouth
What it feels like when
you chew it
Chewing Crackers Discussion
• What was the main texture
(feeling) difference in your mouth
between chewing right away and
waiting 1.5 minutes before
chowing down?
• When the cracker is in your
mouth your saliva starts to break
it down  get’s softer
Food enters the
esophagus which is a
narrow, muscular tube
about 25 centimeters
Food is swallowed by
voluntary action (you
control) of the tongue.
Grab a ruler and have a look
The Trachea (Wind Pipe)
and Esophagus are
connected: – Why does food
not go into lungs?
There is a small flap
consisting of connective
tissue which prevents food
from entering the trachea
when swallowing
The wall of the esophagus
is made up of two layers of
smooth muscles which
push the food down into
the stomach
If a person were to swallow
while being upside down
you could see the muscles
in action.
1) Place your hand over your
throat then swallow
- What do you feel?
2) Turn to someone next to
• Have your partner tilt their
head up
• Watch their neck as they
swallow – reverse roles
The stomach acts as a
storage place for food as
well as a place
of digestion.
It is also described as an
elastic “bag” made
of muscle which expands.
- It can hold up to 4 L of
Chemical Digestion:
Can lead to heart burn - Video
-Stomach cells produce acid
(HCl) which helps break down
-The stomach cells also
secrete mucus to protect its
lining from the acid.
- Sometimes this acid exits
the stomach and enter the
Mechanical Digestion: The
muscles of the stomach wall
contract and expand to
churn food and move it
towards the small
The growling sound you
sometimes here is your
stomach moving.
This is smooth muscle
Bread in bag experiment:
1) Take 1 piece of bread per two students. Rip in half so
each student has ½ of a slice
2) Obtain a small sandwich bag from the front of the room
3) Tear your ½ slice of bread into smaller pieces and place
it into your sandwich bag
(What does this represent?)
4) Your teacher will come around now and pour a small
amount of juice into the bag
5) Close your bag and squish the bread with your fingers
until all of the pieces are really small
(What does this represent?)
6) Put all of the contents of the bag into the garbage
(What does this represent?)
Small Intestine
The small intestine further splits food into smaller
pieces. Most of the nutrients we take in are
absorbed in the small intestine.
Small Intestine Video
Small Intestine
Receives many digestive enzymes from the
pancreas and liver to help break down food
• Moves food using smooth
muscle cell contraction
• The lining of the intestine
secretes protective mucus to
protect it from the enzymes
• Is about 7 m (22 feet 6
inches) long, 2.5 cm (1 inch)
in diameter and has a
surface area of 250 square
meters (2,700 square feet) –
the size of a tennis court!
Large Intestine
• Sometimes called the
Its function is to absorb
water and vitamins from
the remaining food.
Called the large intestine
because it has a much
larger diameter than the
small intestine
• Also stores the remains of
the food that cannot be
absorbed (wastes) before
they are flushed from the
• About 1.5 m (5 feet) long
and 6.5 cm (2.5 inches) in
The rectum acts as a temporary
storage facility for feces before it is
excreted from the body.
Accessory Organs
• The Liver, Pancreas, and Gall
Bladder all help with the digestion
by supplying digestive enzymes.
• The Liver also produces bile which
helps digest fats
• These substances are delivered into
the Small Intestine
- Produces bile which is stored in
the gall bladder.
- Bile is then sent to the small
intestine to break down fats.
Gall Bladder
1) Is involved in supplying enzymes
required for digestion directly into
the small intestine.
2) Secretes a hormone called insulin
directly into the blood stream.
 Insulin causes most of the body's cells to
take up circulating glucose (cell food)
from the blood.
 If insulin is not used effectively,
diabetes can result.
Insulin Video
Review and Revisit
• Name that Digestive
System Organ
1) Liver
2) Esophagus
3) Stomach
4) Pancreas
5) Small Intestine
6) Large Intestine
7) Rectum
The Human
Digestive System
Handout Revisited
What do you already know?
• Complete the Digestive System Handout
to the best of your ability without looking
in any text or your notes.
• Complete the bottom section using
information from this Power Point
Excellent Digestive System Interactive
Activities – Please Click to Visit