Science.7
The Digestive System
Name ______________________________
Date _______________________________
Reading
Essential Questions
1. What are the structures of the digestive system?
2. What is the function of the digestive system?
3. Why do we eat?
Vocabulary
digestive system, digestion,
esophagus, epiglottis, stomach,
chyme, small intestine, large
intestine, absorb
Objectives
1. Identify the structures of the digestive system.
2. Identify the function of the digestive system.
What is Digestion?
Digestion is the breaking down of food into forms that our bodies can
use. Our bodies use food as fuel to provide energy for work, play and
growth. Your digestive system is responsible for changing the food we
eat into energy for our bodies to use.
What is digestion?
How does Digestion begin?
Physical and chemical digestion begins in the mouth. Your teeth help break food apart and the saliva in
your mouth contains enzymes which starts chemical digestion.
Your teeth use ________________________ digestions to break down food while saliva uses
______________________________________ digestion to break down the food.
Where does the food go when we swallow?
After being chewed and swallowed, the food enters the esophagus. The esophagus is a muscular tube that
runs from the mouth to the stomach. It uses rhythmic, wave-like muscle movements (called peristalsis) to
force food from the throat into the stomach. This muscle movement gives us the ability to eat or drink even
when we're upside-down.
Describe the esophagus:
What is peristalsis?
Can you eat or drink standing on your head? Why or why not?
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What about the stomach?
The stomach is a J shaped organ that receives food from the esophagus. Your stomach is located just below
the heart. The stomach makes digestive juices which contain acids and enzymes. They help to break our
food down into a thick liquid. Your stomach is a muscular organ that moves to mix the food with digestive
juices. Food usually remains in the stomach for 2 to 3 hours.
Describe the stomach:
What two substances are present in digestive juices?
Where does the food go after it leaves the stomach?
After leaving the stomach the food enters the small intestine. Your small intestine is a 20-25 foot long tube
that is coiled up in your abdomen. The center of your small intestine is right behind your belly button. The
most important part of digestion takes place in the small intestine. As the thick liquid travels through your
small intestine the nutrients (vitamins, minerals, proteins, carbohydrates and fats) are absorbed by millions
of tiny finger-like objects called villi and sent into your bloodstream where the nutrients can travel to all
your body cells.
What important process takes place in the small intestine?
Which 5 nutrients are absorbed into your bloodstream?
Does the body use all the food we eat?
No, the body does not digest all the food we eat. The undigested food leaves the small intestine and enters
the large intestine. The large intestine is about five feet long so it is shorter than the small intestine. The
large intestine is wider than the small intestine and that is why it is called the large intestine.
Where does the undigested food go when it leaves the small intestine?
Compare the size of the small and large intestine:
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So what does the large intestine do to the undigested food?
The undigested food enters the large intestine as a liquid paste. In the large intestine water is removed from
the liquid paste turning what is left into solid waste. The solid waste then collects in the rectum at the end of
the large intestine and will finally leave the body through an opening called the anus.
Can you guess what happens when your large intestine, for one reason or another, doesn’t absorb all the water
out of the undigested food?
Where is solid waste stored before it leaves the body through the anus?
What causes our stomach to growl?
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 (glucose) 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.
What causes your stomach to growl?
Make sure you eat a HEALTHY breakfast so that your body doesn't run low on fuel (energy) before
lunchtime.
Give an example of a healthy breakfast and a not so healthy breakfast:
Healthy
Not healthy
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