Respiratory
and Circulatory
Systems
Respiratory and Circulatory Systems
• These two systems work together to
provide oxygen and food to cells.
Respiratory System
• Cells of living things require oxygen and food.
• The respiratory system of some animals is
made of the lungs and the passageways that
lead to them. Different structures are used
for gas exchange in other animals, such as the
gills of fish.
Respiratory System
• A tiger’s respiratory system:
• As a tiger breathes in air, it enters through
the nose and mouth. Air travels through a
tube and this tube branches into two smaller
tubes called bronchi. Bronchi have branches
like a tree. These branches empty into thinwalled sacs called alveoli. The walls of the
alveoli are so thin that gases such as oxygen
and carbon dioxide pass through them.
Respiratory and Circulatory Systems
• A tiger’s circulatory system:
• Circulation begins as oxygen-poor blood gets
pumped by the tigers heart to its lungs. In the
lungs, the blood carrying carbon dioxide picks
up oxygen from the air in the alveoli. At the
same time, the blood releases carbon dioxide
(a waste product of cells). As the tiger
breathes out, carbon dioxide leaves the body.
Respiratory and
Circulatory Systems
• The oxygen-rich blood flows back to the heart. The heart
pumps the blood around the body.
• When it reaches the small intestine, it picks up nutrients.
This nutrient-rich and oxygen-rich blood can be delivered
to the tiger’s body cells.
• The blood moves through the body, traveling through
blood vessels. As the blood reaches tiny vessels, or
capillaries, dissolved nutrients and oxygen can pass
through the thin walls and enter cells.
• Cells pass their waste materials back through the
capillaries and into the blood. Oxygen-poor blood gets
pumped back to the heart, and the process continues.
What is the main respiratory
organ in a mammal?
The lungs
How are the bronchi related to
the alveoli?
The bronchi are small tubes
that empty into thin-walled air sacs
called alveoli.
Could the lungs supply oxygen to your body
cells without the circulatory system?
• No
• Why?
• The lungs need a way to transport the oxygen
to other parts of the body.
Let’s name the parts of each organ.
• What is the main function of the lungs?
• The main function of the lungs is to
exchange oxygen and carbon dioxide
with the blood.
Where is the oxygen-poor blood pumped?
.
• Oxygen-poor blood is pumped to
the lungs where the blood picks up
oxygen and rids itself of carbon
dioxide.
What steps does the circulatory system take to
deliver blood to the body?
• The heart pumps oxygen-rich blood to
the body cells. Blood vessels return
carbon dioxide-rich blood to the heart
and then the lungs, where the blood
picks up oxygen and gets rid of carbon
dioxide. The oxygen-rich blood returns to
the heart and is pumped back to the
body cells.
Is the respiratory system part of the
excretory system? Explain.
• The respiratory system is part of the
excretory system because it
removes carbon dioxide from the
body.
• Carbon dioxide is a cellular waste
product.