Chapter 21
The Digestive and Urinary Systems
Table of Contents
Section 1 The Digestive System
Section 2 The Urinary System
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Chapter 21
Section 1 The Digestive System
Bellringer
How does your circulatory system get the nutrients
that it carries to your cells? Describe as best you
can the process that turns food into nutrients that
cells can use.
Record your answers in your science journal.
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Chapter 21
Section 1 The Digestive System
Objectives
• Compare mechanical digestion with chemical
digestion.
• Describe the parts and functions of the digestive
system.
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Digestive Song
by Ms. Smith
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Chapter 21
Section 1 The Digestive System
Digestive System at a Glance
• Your digestive system is a group of organs that
break down food so that it can be used by the body.
• Food passes through the digestive tract. The
digestive tract includes your mouth, pharynx,
esophagus, stomach, small intestine, large intestine,
rectum, and anus.
• The liver, gallbladder, pancreas, and salivary glands
are also part of the digestive system.
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Chapter 21
Section 1 The Digestive System
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Chapter 21
Section 1 The Digestive System
Breaking Down Food
• The breaking, crushing, and mashing of food is
called mechanical digestion.
• In chemical digestion, large molecules are broken
down into nutrients with the aid of enzymes.
•http://youtu.be/xTKjZOhq-_Q
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Chapter 21
Section 1 The Digestive System
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Chapter 21
Section 1 The Digestive System
Digestion Begins in the Mouth
• Teeth With the
help of strong jaw
muscles, teeth
break and grind
food.
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Chapter 21
Section 1 The Digestive System
Digestion Begins in the Mouth, continued
• Saliva contains an enzyme that begins the chemical
digestion of carbohydrates.
• Leaving the Mouth Once the food has been
reduced to a soft mush, the tongue pushes it into the
throat, which leads to a long, straight tube called the
esophagus.
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Chapter 21
Section 1 The Digestive System
The Harsh Environment of the Stomach
• The stomach is a muscular, saclike, digestive organ
attached to the lower end of the esophagus.
• Tiny glands in the stomach produce enzymes and
acid to break food down into nutrients.
• After a few hours of combined mechanical and
chemical digestion, food leaves your stomach as a
soupy mixture called chyme.
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Chapter 21
Section 1 The Digestive System
The Pancreas and Small Intestine
• The Pancreas is an organ located between the
stomach and small intestine. Its makes fluids that
protect the small intestine from the acid in chyme.
• The Small Intestine is a muscular tube that is about
2.5 cm in diameter. In the small intestine, nutrients are
absorbed into the bloodstream through fingerlike
projections called villi.
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Chapter 21
Section 1 The Digestive System
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Chapter 21
Section 1 The Digestive System
The Liver and the Gallbladder
• The liver is a large, reddish brown organ that helps
with digestion by making bile to break up fat.
• Bile is stored in a saclike organ called the
gallbladder, which squeezes the bile into the small
intestine.
• The liver also stores excess nutrients until the body
is ready to absorb them into the bloodstream.
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Chapter 21
Section 1 The Digestive System
The Liver and the Gallbladder, continued
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Chapter 21
Section 1 The Digestive System
The End of the Line
• Material that can’t be absorbed into the blood is
pushed into the large intestine.
• The large intestine absorbs most of the water in
undigested material and changes the liquid into
semisolid waste material called feces, or stool.
• Feces are stored in the rectum until they can be
expelled.
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Chapter 21
Section 1 The Digestive System
The End of the Line, continued
• Feces pass to the
outside of the body
through an opening
called the anus.
• It has taken each of
your meals about 24
hours to make this
journey through your
digestive system.
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Chapter 21
Section 1 The Digestive System
Chemical Digestion
http://youtu.be/jymyhKNOxpg
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Chapter 21
Section 2 The Urinary System
Bellringer
Your blood must be cleaned regularly. Without looking
in your textbook, guess how the body cleans the
blood. Think about what organs might be used to
clean your blood.
Write your answers in your science journal, and then
check your answer against the textbook.
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Chapter 21
Section 2 The Urinary System
Objectives
• Describe the parts and functions of the urinary
system.
• Explain how the kidneys filter blood.
• Describe three disorders of the urinary system.
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Chapter 21
Section 2 The Urinary System
Cleaning the Blood
• The urinary system contains the organs that remove
waste products from your blood.
The Kidneys as Filters
• The kidneys are a pair of organs in the urinary
system that clean the blood and excrete products as
urine. Inside each kidney are more than 1 million
microscopic filters called nephrons.
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Chapter 21
Section 2 The Urinary System
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Chapter 21
Section 2 The Urinary System
Water In, Water Out
• Sweat and Thirst The evaporation of water
sweat cools you down. As the water content of the
blood drops, the salivary glands produce less
saliva, resulting in thirst.
• Antidiuretic Hormone When you get thirsty,
antidiuretic hormone is released. This hormone
signals the kidneys to take water from the
nephrons and return it to the body.
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Chapter 21
Section 2 The Urinary System
Water In, Water Out, continued
• Diuretics Some beverages contain caffeine,
which is a diuretic. Diuretics cause the kidneys to
make more urine, which decreases the amount of
water in the blood.
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Chapter 21
Section 2 The Urinary System
Urinary System Problems
• Bacterial Infections Bacteria can get into the
bladder and ureters through the urethra and cause
painful infections.
• Kidney Stones Salts and other wastes can
collect inside the kidneys and form kidney stones.
• Kidney Disease Damage to nephrons can
prevent normal kidney functioning and can lead to
kidney disease.
•http://youtu.be/aQZaNXNroVY
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End of Chapter 21 Show
Time for Review!!!
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