Download Digestive System - Ms. Montalbano's 7th grade Science

Digestive System
Functions
1. Breaks down the food so
that the body can use it
2. Molecules are absorbed in
the blood and carried
throughout the body
3. Solid wastes are eliminated
from the body
An overview of the process
Digestive Process
Begins
4 Processes of Digestion
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Ingestion: Getting food
into our bodies
Digestion: Breaking down
food into smaller nutrients
Absorption: Getting those
nutrients into our
bloodstream, so that our
cells can use them
Elimination: Getting rid of
solid waste products

Eat it!

Break it Down!

Soak It Up!
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Go to the Bathroom!
2 Types of Digestion
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Digestion means breaking down food into
smaller particles, called nutrients
There are 2 kinds of digestion

Mechanical: Food is broken down by physical
processes (chewing, grinding, moving etc.)
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AND
Chemical: Food is broken down by chemicals
(saliva and acids)
What are nutrients?

Nutrients are things that our bodies need to
survive:
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Water = H2O
Proteins
Carbohydrates
Fats
Vitamins
Minerals
Functions:
1.Mechanically breaks down food by
chewing
2.Wets the food with saliva
3.Chemically breaks down food with
enzymes in saliva
Saliva

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Saliva-fluid that is released to help break
down food
chemical digestion- enzymes in saliva
mechanical digestion- soften the bolus for
easier swallowing
Digestion starts here. The job of the teeth is to
start tearing and crushing the food down into
small enough pieces so that it can fit down
our throats.
Epiglottis
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Epiglottis- A flap called the epiglottis closes
over the top of the trachea (windpipe) when
swallowing, so that food does not enter the
respiratory tract
Mucus helps food go down easier
Functions:
Involuntary smooth muscles
contract and push food toward
the stomach
Peristalsis

The walls of the digestive tract from the
esophagus to the anus are muscular, and
contract rhythmically to move food. The
muscular contractions are called peristalsis
Functions:
• The lining releases digestive juice, which contains:
• Pepsin- Enzyme that breaks down protein
• Hydrochloric Acid (HCl) - Strong Acid to kill any
bacteria you may have ingested
• Thick stomach muscles create a churning motion to
mechanically digest food
• What type of internal stimulus causes vomiting?
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What’s that sound?
Stomach growling occurs when the
stomach receives signals from your
brain to begin digestion but the
stomach is empty.
Your brain might sense you're
running low on energy or even
seeing or smelling something you
want to eat can get things going.
The motion of the stomach muscles
begins, but the organ is hollow.
The movement of the muscles
mixing the acids of the stomach in
the hollow space of the stomach
produces vibrations we hear as
growling, or rumbling, or gurgling.
*See slide note
Pancreas
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Attached near the first
part of the small
intestine
Produces enzymes that
help breaks down
starches, fat and
proteins that goes into
the small intestines
Does not break down
fiber
Liver and Gallbladder
LIVER:
 Breaks down medicines,
other substances and helps
break down nitrogen
 Produces Bile- breaks up
fat particles into small
droplets
Gallbladder-stores the bile
 After you eat the bile
passes through a tube from
the gallbladder into the
small intestine.
Functions:
• Peristalsis (contraction and relaxation of
muscles) to push the food through
• Chemical Digestion through enzymes
• Absorption of nutrients to the blood
Functions:
• Blood Vessels are found within the villi of the
small intestine, here they absorb nutrients and
deliver to the entire body
Drying Out and Exiting the Body
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By the time the food that was eaten leaves the
small intestine, most of the usable nutrients have
been digested and absorbed.
The remaining undigested material moves into the
large intestine where large amounts of water are
removed and the final undigested wastes exit the
body through the rectum (stored waste material)
and anus (comes out).
The large intestines also contain large amounts of
bacteria (some sources say over 700 types!) that
digest some of the remaining material and
produce certain vitamins.
These bacteria also produce GAS as a by product!
So that’s
where it
comes from!
Large Intestine
Appendix
Rectum
Anus
Fun Digestive Facts:
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On average, the stomach produces 2 -2.5 liters of
Hydrochloric Acid daily.
After you eat, it takes usually between 24 and 72 hours in
healthy adults for the complete process of digestion to occur.
In the mouth, food is either cooled or warmed to a more
suitable temperature.
Food stays in your stomach for 2 to 3 hours.
The average male will eat about 50 tons of food during his
lifetime in order to sustain a weight of 150 pounds.
More Fun Digestive Facts
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The liver is the largest and heaviest internal organ of the body
and weighs about 1.6 kilos.
The Liver is the only organ of the body, which has the
capacity to regenerate itself completely even after being
removed almost completely.
Scientists estimate that the average adult releases between 12
and 122 cubic inches of intestinal gas each day. Most of that
gas is made up of hydrogen and methane produced by the
bacteria as they ferment the fiber that was not digested in the
stomach or small intestine.