Lesson 11

When exercising, breathing becomes heavier
and faster. The heart also beats faster. Why
do both systems start to work harder?

As we increase effort, our cells need more
oxygen and nutrients. Blood supplies the
needed nutrients and oxygen.
Oxygen is absorbed into the blood in the
lungs.



Blood is pumped from the right ventricle to
the lungs where it picks up oxygen.
The blood then travels back to the heart
where it is pumped from the left ventricle to
the body cells.

Inside each lung,
there are tiny air
sacs called Alveoli.
The alveoli are
surrounded by
capillaries, which
are very small
blood vessels that
connect the
arteries and veins.

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The alveoli and capillaries have very thin cell
membranes.
The oxygen passes through the membrane of
the capillary into the blood.
Carbon dioxide moves in the opposite
direction. The gas moves from the blood into
the alveolus.

Colour the parts of the respiratory system
green and the parts of the circulatory system
red.

Oxygen moves from the alveoli into
 Blood

Carbon dioxide moves from capillaries into
 Alveoli

Humans eat food and drink fluids to supply
our body cells with more energy.


Nutrients enter the
blood from the small
intestine. The blood
carries nutrients to the
body cells.
Wastes pass from the
cells back into the
blood. The wastes
leave the body.


On the inside
wall of the small
Intestine, there
are many villi,
which look like
tiny fingers.

Inside the villi, there are
many capillaries. The
villi and capillaries have
very thin cell
membranes.

The nutrients pass
through the villi into the
capillaries.

Waste products from
the body cells pass into
the capillaries before
the body gets rid of
them.

Colour the parts of the digestive system
yellow and the parts of the circulatory system
red.

How do nutrients pass into the blood?
 They pass through the villi into the capillaries

In what way are villi and alveoli similar?
 They are both use capillaries to transport
materials that cells need.
 They both use capillaries to get rid of waste.