Download What is the digestive system?

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Your cells need a lot of energy for daily
activities.
Cells use nutrients, which are substances in
food, for energy, growth, maintenance, and
repair.
The digestive system breaks down the food
you eat into nutrients that can be used as
building materials and that can provide
energy for cells.
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Digestion is the process of breaking down
food into a form that can pass from the
digestive system into the bloodstream.
There are two types of digestion: mechanical
and chemical.
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Mechanical Digestion
Is the breaking, crushing, and mashing of
food.
Ex: Chewing is a type of mechanical
digestion. Chewing creates small pieces of
food that are easier to swallow and digest
than large pieces are.
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Chemical Digestion
Is the process in which large molecules of food
are broken down into smaller molecules so that
they can pass into the bloodstream.
An enzyme is a chemical that the body uses to
break down large molecules into smaller
molecules.
Enzymes act like chemical scissors, they “cut
up” large molecules into smaller pieces.
*Without mechanical digestion, chemical
digestion would take days instead of hours*
In your mouth, teeth grind food
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mechanical
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chemical
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In the small intestine, most nutrients are
broken down by enzymes
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mechanical
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chemical
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In your mouth, teeth grind food
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mechanical
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chemical
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In the small intestine, most nutrients are
broken down by enzymes
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mechanical
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chemical
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The Mouth
The Esophagus
Stomach
Small Intestine
Large Intestine
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The Mouth
Digestion begins in the mouth with both
mechanical and chemical digestion.
Teeth, with the help of the jaw, break and
crush food.
As you chew, food is moistened by saliva.
Saliva contains many substances, including
an enzyme that begins the chemical
digestion of starches in food.
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The Esophagus
Once food has been chewed, it is swallowed
and moves through the throat and a long
tube called the esophagus.
Waves of muscle contractions move food into
the stomach.
Ex: muscle moves food along the same
way you move toothpaste from the
bottom of the tube with your thumbs
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Stomach
The stomach is a muscular
bag that crushes food and
contains acids and enzymes
for killing bacteria and
breaking down protein.
The stomach wall contains
layers of muscle so the
stomach can churn and mix
food.
This is the final step of
mechanical digestion.
Food sits in the stomach for
a few hours before moving
to…..
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Small Intestine
The small intestine is a muscular tube were
most chemical digestion takes place.
Most nutrients are absorbed in the small
intestine as well.
Food travels from the stomach into the small
intestine in the form of chyme.
Chyme is food reduced to a soupy mixture
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Large Intestine
After food moves
through the small
intestine, it moves to
the large intestine.
In the large intestine,
water and nutrients are
absorbed.
Most solid material
that remains is waste
Waste is compacted
and stored until the
body eventually
eliminates it.
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After nutrients are
broken down, they are
absorbed into the
blood stream and used
by cells
Small Intestine
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Removes water from
mostly-digested foods,
absorbs vitamins, and
turns food waste into
semi-solid waste.
Large Intestine
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Pancreas-makes fluids that break down every
type of material found in foods
Ex: these include proteins, carbohydrates, fats,
and nucleic acids
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Liver-makes and releases a mixture called
bile that is stored in the gall bladder
◦ Bile breaks up large fat droplets into very small fat
droplets
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HOW LONG ARE YOUR INTESTINES? At least
25 feet in an adult. Be glad you're not a fullgrown horse -- their coiled-up intestines are
89 feet long!
Chewing food takes from 5-30 seconds
Swallowing takes about 10 seconds
Food sloshing in the stomach can last 3-4
hours
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It takes 3 hours for food to move through the
intestine
Food drying up and hanging out in the large
intestine can last 18 hours to 2 days!
Americans eat about 700 million pounds of
peanut butter.
Americans eat over 2 billion pounds of
chocolate a year.
In your lifetime, your digestive system may
handle about 50 tons!!
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