The Digestive and Excretory
Systems
In this lesson, you will Learn About…
 How your body digests food.
 How your body removes waste products.
The Digestive and Excretory
Systems
The Vocabulary terms in this lesson are:
 Digestion.
 Pancreas.
 Digestive system.
 Excretion.
 Saliva.
 Excretory system.
 Small intestine.
 Colon.
 Liver.
 Kidneys.
Turning Food into Fuel
When you eat, your body’s digestive
system breaks the food down into smaller
parts so it can use the nutrients in the food
for fuel. This is the process of digestion.
Mouth
Crushing
and Grinding
Stomach
Small
Intestine
Useful
Chemical
Material
Breakdown Extracted
Colon
Water
Removal
Waste
Elimination
How Digestion Begins
Saliva is a digestive juice produced by the
salivary glands in your mouth. It starts to
flow as a physical signal from your body
that it is ready to begin the digestive
process.
When you chew your food and swallow it,
your body initiates the digestive process.
Chewing and Swallowing
teeth tear and grind the
1 The
food into small shreds or
chunks.
salivary glands produce
2 The
saliva. Enzymes in saliva
begin the chemical
breakdown of
carbohydrates.
you swallow, a flap of
3 When
skin called the epiglottis
the food is
4 Once
swallowed, it
enters the
esophagus.
closes off the trachea to keep
food from entering it. At the
same time, the uvula closes
off the airway to the nose.
Organs of the Digestive System
1 Acid and enzymes in
the stomach break
down food until it
resembles a thin soup
called chyme.
2 Next the food
moves to the
small intestine.
3
The liver
secretes bile to
help digest fats.
4 After the liver
produces bile, it
sends it to the
gallbladder.
5 The pancreas
produces
pancreatic juice
to break down
proteins,
carbohydrates,
and fats.
6 Nutrients from
the digested
material pass
through the
small intestine.
Removing Wastes from the Body
Some foods that you eat contain
substances that the body cannot use.
During the digestive process, these
wastes are separated out.
The wastes are removed from the body
through a process called excretion. The
major organs of the excretory system are
the kidneys, bladder, and colon.
Eliminating Liquid Wastes
1
The kidneys filter water
and waste materials
from the blood.
2
The kidneys send the
urine to the bladder
through two tubes called
ureters.
3
The urine is stored in the
bladder.
4
Urine passes out of the
body through a tube called
the urethra.
Solid Wastes
Solid wastes are made up of foods that
your body cannot break down, including
fiber.
After digestion, the body sends a mixture
of water and undigested solid wastes
into the colon.
Most of the water is absorbed by the
colon and returned to the body. The
remaining solid wastes become material
called feces.
Caring for Your Digestive and
Excretory Systems
To keep the digestive and excretory
systems working well:
 Eat a balanced diet that is based on the Food
Guide Pyramid.
 Eat plenty of foods that are low in fat and high
in fiber.
 Eat at regular times each day.
 Drink eight to ten glasses of water every day.
 Take care of your teeth.
 Stay active.
Reviewing Terms and Facts
1.Define the term digestion.
Digestion is the process by which the body
breaks down food into smaller components
that can be absorbed by the bloodstream and
sent to each cell in the body.
Reviewing Terms and Facts
2.Identify the major organs of the
excretory system.
 Kidneys
 Bladder
 Colon
Thinking Critically
3.Describe possible consequences for the
rest of the body if the digestive system is
not working properly.
Vocabulary Review
Digestion is the process by which the body
breaks down food into smaller
components that can be absorbed by the
bloodstream and sent to each cell in the
body.
Vocabulary Review
The digestive system is a group of organs
that work together to break down foods
into substances that the cells can use.
Vocabulary Review
Saliva is a digestive juice produced by the
salivary glands in the mouth.
Vocabulary Review
The small intestine is a coiled tube, about
20 feet long, where most of the digestive
process takes place.
Vocabulary Review
The liver, the body’s largest gland,
secretes a liquid called bile that helps to
digest fats.
Vocabulary Review
The pancreas is a gland that helps the
small intestine by producing pancreatic
juice, a blend of enzymes that breaks
down proteins, carbohydrates, and fats.
Vocabulary Review
Excretion is the process by which the body
gets rid of waste materials.
Vocabulary Review
The excretory system is the system that
removes wastes from the body and
controls water balance.
Vocabulary Review
The colon is a storage tube for solid
wastes.
Vocabulary Review
The kidneys are a pair of organs that filter
water and waste materials from the blood.