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Circulatory system
The double circulatory system
1. The first one pumps
deoxygenated blood which is
blood without oxygen. The blood
returns to the heart.
2. The second one pumps
oxygenated blood around all the
other organs of the body. The
blood gives up its oxygen at the
body cells and deoxygenated
blood returns to the heart to be
pumped out of the lungs again…read more

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The Heart
1. The heart is a pumping organ that keeps the blood flowing around the body, the walls of
the heart are mostly made of muscle tissue
2. The heart has valves to make sure the blood flows in the right direction
3. This is how the heart uses its four chambers (right atrium, right ventricle, left atrium and
the left ventricle…read more

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How the Heart works?
1. Blood flows into he two atria from he
vena cava and the pulmonary vein
2. The atria contract, pushing the
blood into the ventricles
3. The ventricles contract, forcing the
blood into the pulmonary artery and
the aorta, and out of the heart
4. The blood then flows to the organs
through arteries and returns through
the veins
5. The atria fill again and the whole
cycle starts over again…read more

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Blood Vessels
Carry blood away from the heart (always oxygenated apart from the pulmonary artery which
goes to the lungs)
Have thick muscular walls
Have small passageways for blood (internal lumen)
Contain blood under high pressure
Carry blood to the heart (always de-oxygenated apart from the pulmonary vein which goes
from the lungs to the heart)
Have thin walls
Have larger internal lumen
Contain blood under low pressure
Have valves to prevent blood flowing backwards
Found in the muscles and lungs
Microscopic ­ one cell thick
Very low blood pressure
Where gas exchange takes place. Oxygen passes through the capillary wall and into the
tissues, carbon dioxide passes from the tissues into the blood…read more

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Red Blood Cells
Contain red pigment called
haemoglobin to carry oxygen to
the cells.
Thin outer membrane to let
oxygen diffuse through easily.
Shape increases the surface
area to allow more oxygen to be
absorbed efficiently. No
nucleus, so the whole cell is full
of haemoglobin.
In the lungs, the haemoglobin
combines with the oxygen to
become oxyhaemoglobin. In
body tissues, the reverse
happens- oxyhaemoglobin splits
into haemoglobin and oxygen,
to release oxygen to the cells…read more

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