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The circulatory system is made up of the
vessels and the muscles that help and control the flow of
the blood around the body. This process is called
circulation. The main parts of the system are the heart,
arteries, capillaries and veins.
As blood begins to circulate, it leaves
the heart from the left ventricle and goes into the aorta.
The aorta is the largest artery in the body. The blood
leaving the aorta is full of oxygen.
This is important for the cells in the brain and the body to
do their work. The oxygen rich blood travels throughout the
body in its system of arteries into the smallest arterioles.
On its way back to the heart, the blood
travels through a system of veins. As it reaches the lungs,
the
carbon dioxide (a waste product)
is removed from the blood and replace with fresh oxygen that
we have inhaled
through the lungs.
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Veins and
Arteries
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Arteries
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Arteries are tough, elastic tubes that
carry blood away from the heart. As the arteries move away
from the heart, they divide into smaller vessels. The
largest arteries are about as thick as a thumb. The smallest
arteries are thinner than hair. These thinner arteries are
called arterioles. Arteries carry bright red blood! The
color comes from the oxygen
that it carries.
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Veins
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Veins carry the blood to the heart. The
smallest veins, also called venules, are very thin. They
join larger veins that open into the heart. The veins carry
dark red blood that doesn't have much oxygen. Veins have
thin walls. They don't need to be as strong as the arteries
because as blood is returned to the heart, it is under less
pressure.
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Lizards don't have hair or
feathers to keep warm and can't sweat to cool down.
They are
COLD-BLOODED,
which means their inside temperature is the same as
the temperature of the outside air. | |
2.
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Heart
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Did you know that your heart is the
strongest muscle? Your heart is divided into two sides. The
right side pumps blood to your lungs
where it picks up oxygen. The left side pumps oxygen-soaked
blood out to your body. They do not work on their own, but
together as a team. The body's blood is circulated through
the heart more than 1,000 times per day. Between five and
six thousand quarts of blood are pumped each day. Your heart
is about the same size as your fist.
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Your heart's job is to pump
blood around your body. Its muscles contract and
squeeze out blood. The left-hand side pumps blood
from the lungs to the rest of your body. The
right-hand side pumps stale blood from your body
back to your lungs
for a fresh supply of oxygen. | |
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What is
Blood?
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Blood is thicker than water and has a
little bit salty taste. In an adults body there is 10.6
pints of blood circulating around. In their blood there is
billions of living blood cells floating in a liquid called
plasma. If you took a small sample of this blood and poured
it into a test tube and then put it in a machine called a
centrifuge, you would be able to see the layers of this
blood. This machine spins the blood around so fast that it
separates the red blood cells, from the white blood cells,
from the platelets. The red blood cells sink to the bottom
because they are the heavier, more solid parts, but the
plasma remains at the top because it is lighter. The plasma
is 95% water and the other 5% is made up of dissolved
substances including salts.
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Horned toads are small lizards
with toad-like faces. When cornered the horned toad
will shoot small jets of blood from its
eyes. | |
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